Evidence used
- No CISA KEV confirmation is currently recorded.
- Exploitation requires an existing local or physical foothold with privileges.
- EPSS is 0.15% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2025
CVE-2025-39994High confidence
media: tuner: xc5000: Fix use-after-free in xc5000_release
Linux · Linux
7.3HighCVSS 3.1
Patch only the product branches with a verified fix
Fix availability varies by productHigh technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 20 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityHigh→Operational priority:Medium, lowered one band.downgradedsince 5 Aug 2026
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict local access and enforce least privilege on affected hosts.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs Linux Linux and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Remediation availability differs by product scope
Verified remediation exists for at least one product or source, but 20 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- Canonical Ubuntu Security: 20 affected package states with no published fix
Distribution package intelligence
24 package statesRelease-specific package status
Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.
Package result overrides the generic status
BlackTree has verified remediation for at least one product or source, but the relevant distribution still reports no fixed package for 20 affected package states shown here. Treat those rows as affected with no fix until that distribution publishes a fixed version.
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
| Distribution release | Source package | Vendor state | Fixed version | Evidence |
|---|---|---|---|---|
| Debian trixietrixie · source | linux | Vendor fix publishedDebian records a fixed source-package version for this release. | 6.12.57-1 | Debian Security Tracker ↗Source updated 7 Oct 2026 |
| Debian bookwormbookworm · source | linux | Vendor fix publishedDebian records a fixed source-package version for this release. | 6.1.158-1 | Debian Security Tracker ↗Source updated 7 Oct 2026 |
| Debian forkyforky · source | linux | Vendor fix publishedDebian records a fixed source-package version for this release. | 6.16.11-1 | Debian Security Tracker ↗Source updated 7 Oct 2026 |
| Debian sidsid · source | linux | Vendor fix publishedDebian records a fixed source-package version for this release. | 6.16.11-1 | Debian Security Tracker ↗Source updated 7 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-aws | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-azure | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-azure-fde | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-azure-nvidia | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-gcp | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-gke | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-gkeop | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-ibm | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-lowlatency | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-nvidia | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-nvidia-lowlatency | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-nvidia-tegra | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-oem-6.11 | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-oracle | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-raspi | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-raspi-realtime | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-realtime | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-riscv | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | linux-xilinx | Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 6 Oct 2026 |
Direct vendor intelligence
1 currentAuthoritative vendor CSAF and VEX advisories
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
CVE-2025-39994 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitykernel: Linux kernel: Use-after-free in xc5000 tuner driver due to race condition
The vendor explicitly identifies these products or versions as containing the fix.
- bpftool-0:4.18.0-553.171.1.el8_10.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-0:4.18.0-553.171.1.el8_10.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-0:4.18.0-553.171.1.el8_10.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-0:4.18.0-553.171.1.el8_10.x86_64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-debuginfo-0:4.18.0-553.171.1.el8_10.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-debuginfo-0:4.18.0-553.171.1.el8_10.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-debuginfo-0:4.18.0-553.171.1.el8_10.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-debuginfo-0:4.18.0-553.171.1.el8_10.x86_64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-0:4.18.0-553.171.1.el8_10.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-0:4.18.0-553.171.1.el8_10.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-0:4.18.0-553.171.1.el8_10.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-0:4.18.0-553.171.1.el8_10.src as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- Summary
- A use-after-free flaw was identified in the Linux kernel’s media tuner (xc5000) driver. In the vulnerable code path, xc5000_release() calls cancel_delayed_work() to cancel a pending delayed work item (timer_sleep) without guaranteeing that the work handler has fully completed. Under a race condition, the underlying xc5000_priv structure may be freed while the delayed work item is still active, potentially resulting in a use-after-free when the work item subsequently dereferences the freed memory.
- Remediation
- For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 The system must be rebooted for this update to take effect. Red Hat recommends treating all kernel errata as security-relevant. Given the kernel's fundamental role, any bug has a higher chance of impacting system security, even if that impact only becomes clear after a fix is published. Therefore, Red Hat prioritizes delivering fixes that improve our customers' overall security posture. Because of this proactive approach, a patch may be associated with a CVE assignment at a future date. Retroactive CVE assignments are always documented in the corresponding errata and on Red Hat's CVE pages. We strongly advise against delaying updates, as doing so may leave your system exposed when protections are already available.
High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 20 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
Fix availability varies by product01
What, why and how
In the Linux kernel, the following vulnerability has been resolved: media: tuner: xc5000: Fix use-after-free in xc5000_release The original code uses cancel_delayed_work() in xc5000_release(), which does not guarantee that the delayed work item timer_sleep has fully completed if it was already running. This leads to use-after-free scenarios where xc5000_release() may free the xc5000_priv while timer_sleep is still active and attempts to dereference the xc5000_priv. A typical race condition is illustrated below: CPU 0 (release thread) | CPU 1 (delayed work callback) xc5000_release() | xc5000_do_timer_sleep() cancel_delayed_work() | hybrid_tuner_release_state(priv) | kfree(priv) | | priv = container_of() // UAF Replace cancel_delayed_work() with cancel_delayed_work_sync() to ensure that the timer_sleep is properly canceled before the xc5000_priv memory is deallocated. A deadlock concern was considered: xc5000_release() is called in a process context and is not holding any locks that the timer_sleep work item might also need. Therefore, the use of the _sync() variant is safe here. This bug was initially identified through static analysis. [hverkuil: fix typo in Subject: tunner -> tuner]
What
In the Linux kernel, the following vulnerability has been resolved: media: tuner: xc5000: Fix use-after-free in xc5000_release The original code uses cancel_delayed_work() in xc5000_release(), which does not guarantee that the delayed work item timer_sleep has fully completed if it was already running. This leads to use-after-free scenarios where xc5000_release() may free the xc5000_priv while timer_sleep is still active and attempts to dereference the xc5000_priv. A typical race condition is illustrated below: CPU 0 (release thread) | CPU 1 (delayed work callback) xc5000_release() | xc5000_do_timer_sleep() cancel_delayed_work() | hybrid_tuner_release_state(priv) | kfree(priv) | | priv = container_of() // UAF Replace cancel_delayed_work() with cancel_delayed_work_sync() to ensure that the timer_sleep is properly canceled before the xc5000_priv memory is deallocated. A deadlock concern was considered: xc5000_release() is called in a process context and is not holding any locks that the timer_sleep work item might also need. Therefore, the use of the _sync() variant is safe here. This bug was initially identified through static analysis. [hverkuil: fix typo in Subject: tunner -> tuner]
Why
The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.
How
An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
In the Linux kernel, the following vulnerability has been resolved: media: tuner: xc5000: Fix use-after-free in xc5000_release The original code uses cancel_delayed_work() in xc5000_release(), which does not guarantee that the delayed work item timer_sleep has fully completed if it was already running. This leads to use-after-free scenarios where xc5000_release() may free the xc5000_priv while timer_sleep is still active and attempts to dereference the xc5000_priv. A typical race condition is illustrated below: CPU 0 (release thread) | CPU 1 (delayed work callback) xc5000_release() | xc5000_do_timer_sleep() cancel_delayed_work() | hybrid_tuner_release_state(priv) | kfree(priv) | | priv = container_of() // UAF Replace cancel_delayed_work() with cancel_delayed_work_sync() to ensure that the timer_sleep is properly canceled before the xc5000_priv memory is deallocated. A deadlock concern was considered: xc5000_release() is called in a process context and is not holding any locks that the timer_sleep work item might also need. Therefore, the use of the _sync() variant is safe here. This bug was initially identified through static analysis. [hverkuil: fix typo in Subject: tunner -> tuner]
Why
The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.
How
An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- local access → vulnerable operation → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Local
- Privileges required
- Low: a basic authenticated account is required
- User interaction
- Required interaction required
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration. - CWE not yet assigned
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:HCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UIRequiredUser interaction: Another user must perform an action for exploitation to succeed.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.- Post-exploitation / living off the land
- The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Fix availability varies by product
- Fixed
- bpftool-0:4.18.0-553.171.1.el8_10.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-0:4.18.0-553.171.1.el8_10.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-0:4.18.0-553.171.1.el8_10.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-0:4.18.0-553.171.1.el8_10.x86_64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-debuginfo-0:4.18.0-553.171.1.el8_10.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-debuginfo-0:4.18.0-553.171.1.el8_10.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-debuginfo-0:4.18.0-553.171.1.el8_10.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- bpftool-debuginfo-0:4.18.0-553.171.1.el8_10.x86_64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-0:4.18.0-553.171.1.el8_10.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-0:4.18.0-553.171.1.el8_10.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-0:4.18.0-553.171.1.el8_10.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-0:4.18.0-553.171.1.el8_10.src as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-0:4.18.0-553.171.1.el8_10.x86_64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-abi-stablelists-0:4.18.0-553.171.1.el8_10.noarch as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-core-0:4.18.0-553.171.1.el8_10.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-core-0:4.18.0-553.171.1.el8_10.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-core-0:4.18.0-553.171.1.el8_10.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-core-0:4.18.0-553.171.1.el8_10.x86_64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-debug-0:4.18.0-553.171.1.el8_10.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-debug-0:4.18.0-553.171.1.el8_10.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-debug-0:4.18.0-553.171.1.el8_10.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-debug-0:4.18.0-553.171.1.el8_10.x86_64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-debug-core-0:4.18.0-553.171.1.el8_10.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-debug-core-0:4.18.0-553.171.1.el8_10.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-debug-core-0:4.18.0-553.171.1.el8_10.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-debug-core-0:4.18.0-553.171.1.el8_10.x86_64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-debug-debuginfo-0:4.18.0-553.171.1.el8_10.aarch64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-debug-debuginfo-0:4.18.0-553.171.1.el8_10.ppc64le as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-debug-debuginfo-0:4.18.0-553.171.1.el8_10.s390x as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- kernel-debug-debuginfo-0:4.18.0-553.171.1.el8_10.x86_64 as a component of Red Hat Enterprise Linux BaseOS (v. 8)
- and 120 more
- Action
- Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
- Workaround
- No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04
Evidence and provenance
Published 15 Oct 2025 · Last source change 5 Aug 2026, 12:06 UTC · CWE not yet assigned
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2025-34579
Product sourceCNA
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceUnavailable
NVD statusNVD not scheduled
Missing structured fields: CWE classification. Missing data is not evidence of low risk; review the primary advisory.
Material change intelligence
View recent updates ↗What changed after publication
No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.
CVE published
Fixed release or patch reference recorded
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.