Evidence used
- No CISA KEV confirmation is currently recorded.
- EPSS is 0.45% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2026-66032High confidence
libssh2 Double-Free Heap Corruption via sftp_open()
libssh2 · libssh2
8.7HighCVSS 4.0
Within 7 days
Patch availableHigh technical severity; prioritise exposed affected systems while verifying vendor guidance.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityHigh→Operational priority:High, unchanged from published severity.unchanged
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs libssh2 libssh2 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.
Distribution package intelligence
5 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.
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 | libssh2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 1.11.1-1+deb13u2 | Debian Security Tracker ↗Source updated 6 Oct 2026 |
| Debian bookwormbookworm · source | libssh2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 1.10.0-3+deb12u1 | Debian Security Tracker ↗Source updated 6 Oct 2026 |
| Debian forkyforky · source | libssh2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 1.11.1-5 | Debian Security Tracker ↗Source updated 6 Oct 2026 |
| Debian sidsid · source | libssh2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 1.11.1-5 | Debian Security Tracker ↗Source updated 6 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | libssh2 | Vendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree. | 1.11.0-4.1ubuntu0.24.04.4 | Canonical Ubuntu Security ↗Source updated 5 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-2026-66032 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitylibssh2: libssh2: Arbitrary code execution via double-free in SFTP session
The vendor explicitly identifies these products as affected by this CVE.
- libssh2 as a component of Red Hat Enterprise Linux 6
- libssh2-devel as a component of Red Hat Enterprise Linux 6
- libssh2-docs as a component of Red Hat Enterprise Linux 6
- libssh2.src as a component of Red Hat Enterprise Linux 6
- Summary
- A flaw was found in libssh2. A malicious SSH (Secure Shell) server can exploit a double-free vulnerability in the sftp_open() function. This flaw allows the server to corrupt the heap memory of an authenticated client when it opens an SFTP (SSH File Transfer Protocol) session. This heap corruption can lead to arbitrary code execution on the client system, giving the attacker control over the affected system.
- 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
High technical severity; prioritise exposed affected systems while verifying vendor guidance.
Patch available01
What, why and how
libssh2 through 1.11.1, fixed in commit 5e47761, contains a double-free vulnerability in the sftp_open() function in src/sftp.c that allows a malicious SSH server to corrupt the heap of any authenticated client opening an SFTP session. When a server responds to SSH_FXP_OPEN with SSH_FXP_STATUS containing FX_OK, the response data buffer is freed, and if a subsequent sftp_packet_require() call returns a specific error such as LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, the same pointer is freed a second time, enabling tcache dup conditions on glibc systems that allow overlapping allocations and function pointer overwrites.
What
libssh2 through 1.11.1, fixed in commit 5e47761, contains a double-free vulnerability in the sftp_open() function in src/sftp.c that allows a malicious SSH server to corrupt the heap of any authenticated client opening an SFTP session. When a server responds to SSH_FXP_OPEN with SSH_FXP_STATUS containing FX_OK, the response data buffer is freed, and if a subsequent sftp_packet_require() call returns a specific error such as LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, the same pointer is freed a second time, enabling tcache dup conditions on glibc systems that allow overlapping allocations and function pointer overwrites.
Why
The product calls free() twice on the same memory address.
How
An attacker operating through a network path may attempt exploitation when the stated preconditions are met. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
libssh2 through 1.11.1, fixed in commit 5e47761, contains a double-free vulnerability in the sftp_open() function in src/sftp.c that allows a malicious SSH server to corrupt the heap of any authenticated client opening an SFTP session. When a server responds to SSH_FXP_OPEN with SSH_FXP_STATUS containing FX_OK, the response data buffer is freed, and if a subsequent sftp_packet_require() call returns a specific error such as LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, the same pointer is freed a second time, enabling tcache dup conditions on glibc systems that allow overlapping allocations and function pointer overwrites.
Why
The product calls free() twice on the same memory address.
How
An attacker operating through a network path may attempt exploitation when the stated preconditions are met. 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
- a network path → Double Free → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Network
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- Passive interaction required
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Not a CVSS 4.0 base metric
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-415 ↗
CWE-415: Double Free. The product calls free() twice on the same memory address.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:NCommon Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing privileges.UIPassiveUser interaction: A user must unknowingly interact with the vulnerable system.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
- No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
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. - Patch available
- Affected
- Fixed
- libssh2-0:1.8.0-4.el7_9.2.i686 as a component of Red Hat Enterprise Linux Server (v. 7 ELS)
- libssh2-0:1.8.0-4.el7_9.2.ppc as a component of Red Hat Enterprise Linux Server (v. 7 ELS)
- libssh2-0:1.8.0-4.el7_9.2.ppc64 as a component of Red Hat Enterprise Linux Server (v. 7 ELS)
- libssh2-0:1.8.0-4.el7_9.2.ppc64le as a component of Red Hat Enterprise Linux Server (v. 7 ELS)
- libssh2-0:1.8.0-4.el7_9.2.s390 as a component of Red Hat Enterprise Linux Server (v. 7 ELS)
- libssh2-0:1.8.0-4.el7_9.2.s390x as a component of Red Hat Enterprise Linux Server (v. 7 ELS)
- libssh2-0:1.8.0-4.el7_9.2.src as a component of Red Hat Enterprise Linux Server (v. 7 ELS)
- libssh2-0:1.8.0-4.el7_9.2.x86_64 as a component of Red Hat Enterprise Linux Server (v. 7 ELS)
- libssh2-main@aarch64 as a component of Red Hat Hardened Images
- libssh2-main@noarch as a component of Red Hat Hardened Images
- libssh2-main@src as a component of Red Hat Hardened Images
- libssh2-main@x86_64 as a component of Red Hat Hardened Images
- Action
- For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
- Workaround
- No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04
Evidence and provenance
Published 24 Jul 2026 · Last source change 28 Jul 2026, 01:06 UTC · CWE-415 · Double Free
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-2026-48719
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched
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.
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.