Evidence used
- No CISA KEV confirmation is currently recorded.
- Exploitation requires an existing local or physical foothold with privileges.
- EPSS is 0.10% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2025-14963High confidence
A vulnerability identified in the HX Agent driver file fekern.sys allowed a threat actor with local user access the ability to gain elevated system privileges
Trellix · Endpoint HX Agent (xAgent)
6.2MediumCVSS 4.0
Scheduled
Fix not verifiedMedium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityMedium→Operational priority:Low, lowered one band.downgradedsince 26 Feb 2026
Compensating controls
- 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 Trellix Endpoint HX Agent (xAgent) and falls inside the recorded affected range.
- Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
Fix not verified01
What, why and how
A vulnerability identified in the HX Agent driver file fekern.sys allowed a threat actor with local user access the ability to gain elevated system privileges. Utilization of a Bring Your Own Vulnerable Driver (BYOVD) was leveraged to gain access to the critical Windows process memory lsass.exe (Local Security Authority Subsystem Service). The fekern.sys is a driver file associated with the HX Agent (used in all existing HX Agent versions). The vulnerable driver installed in a product or a system running a fully functional HX Agent is, itself, not exploitable as the product’s tamper protection restricts the ability to communicate with the driver to only the Agent’s processes.
What
A vulnerability identified in the HX Agent driver file fekern.sys allowed a threat actor with local user access the ability to gain elevated system privileges. Utilization of a Bring Your Own Vulnerable Driver (BYOVD) was leveraged to gain access to the critical Windows process memory lsass.exe (Local Security Authority Subsystem Service). The fekern.sys is a driver file associated with the HX Agent (used in all existing HX Agent versions). The vulnerable driver installed in a product or a system running a fully functional HX Agent is, itself, not exploitable as the product’s tamper protection restricts the ability to communicate with the driver to only the Agent’s processes.
Why
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
How
An attacker operating through local access may attempt exploitation with elevated privileges. If successful, the issue may gain additional privileges.
What
A vulnerability identified in the HX Agent driver file fekern.sys allowed a threat actor with local user access the ability to gain elevated system privileges. Utilization of a Bring Your Own Vulnerable Driver (BYOVD) was leveraged to gain access to the critical Windows process memory lsass.exe (Local Security Authority Subsystem Service). The fekern.sys is a driver file associated with the HX Agent (used in all existing HX Agent versions). The vulnerable driver installed in a product or a system running a fully functional HX Agent is, itself, not exploitable as the product’s tamper protection restricts the ability to communicate with the driver to only the Agent’s processes.
Why
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
How
An attacker operating through local access may attempt exploitation with elevated privileges. If successful, the issue may gain additional privileges.
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 → Improper Input Validation → gain additional privileges
- Attack surface
- Local
- Privileges required
- High: elevated access is required
- User interaction
- None
- Attack complexity
- High: exploitation depends on specific conditions
- Security boundary
- Not a CVSS 4.0 base metric
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-20 ↗
CWE-20: Improper Input Validation. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:4.0/AV:L/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:PCommon Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.
AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.ATPresentAttack requirements: A particular deployment or execution condition must be present.PRHighPrivileges required: The attacker needs elevated or administrative privileges.UINoneUser interaction: No action by another user is required.VCHighVulnerable-system confidentiality: A successful attack can cause a major loss.VIHighVulnerable-system integrity: A successful attack can cause a major loss.VAHighVulnerable-system availability: A successful attack can cause a major loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.- 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 not verified
- Affected
- Endpoint HX Agent (xAgent): 36.30.0-17, 35.31.0-37, 34.x, 33.x and 30.x
- Fixed
- No fixed version is explicitly recorded in the structured CVE data.
- Action
- No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
- Workaround
- No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04
Evidence and provenance
Published 24 Feb 2026 · Last source change 26 Feb 2026, 14:44 UTC · CWE-20 · Improper Input Validation
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-2025-208089
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD enrichment underway
Core structured fields are present and their contributing authorities are shown above.
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.
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.