Skip to main content

Public vulnerability disclosure

Investigate in Cyber

Open

CVE-2026-66032

libssh2 Double-Free Heap Corruption via sftp_open()

publishedCWE-415

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.

Technical severity8.7 highCVSS 4.0 · CNA: VulnCheck

Published2026-07-24Source updated 2026-11-10

Collected2026-11-103 attributed sources

Fixes and workarounds

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: CNA: VulnCheck

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: CNA: VulnCheck

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: [email protected]

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: [email protected]

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: [email protected]

Affected products and versions

Affected products, source version ranges and reporting authorities
Product	Versions	Authority
libssh2 libssh2 `libssh2/libssh2` github	≥ 0; ≤ 1.11.1 (affected, semver) 5e4776146552d898b9c0e1b313cd093fa8dc92d0 (unaffected, git) Other versions: affected	CNA: VulnCheck
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP

Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.

NVD applicability configurations (1)

These expressions retain AND/OR operators, negation, and required environmental products. A listed product is not sufficient to establish exposure when additional conditions apply.

[
  {
    "negate": false,
    "nodes": [
      {
        "cpeMatch": [
          {
            "criteria": "cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*",
            "versionEndIncluding": "1.11.1",
            "vulnerable": true
          }
        ],
        "negate": false,
        "operator": "OR"
      }
    ],
    "operator": "OR"
  }
]

CVSS assessments

CVSS scores, vectors and reporting authorities
Version / score	Vector	Authority
4.0 / 8.7 high	`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`	CNA: VulnCheck
3.1 / 8.8 high	`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`	CNA: VulnCheck
4.0 / 8.7 high	`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X`	NVD: [email protected]
3.1 / 8.8 high	`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`	NVD: [email protected]

Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

References

https://github.com/libssh2/libssh2/pull/2180CNA: VulnCheck · issue-tracking, patch
https://github.com/libssh2/libssh2/commit/5e4776146552d898b9c0e1b313cd093fa8dc92d0CNA: VulnCheck · patch
https://www.vulncheck.com/advisories/libssh2-double-free-heap-corruption-via-sftp-openCNA: VulnCheck · third-party-advisory
https://cert-portal.siemens.com/productcert/html/ssa-457936.htmlADP: siemens-SADP
https://github.com/libssh2/libssh2/commit/5e4776146552d898b9c0e1b313cd093fa8dc92d0[email protected] · Patch
https://github.com/libssh2/libssh2/pull/2180[email protected] · Issue Tracking, Patch
https://www.vulncheck.com/advisories/libssh2-double-free-heap-corruption-via-sftp-open[email protected] · Patch, Third Party Advisory

For agents and automation

Read public disclosures for free as Markdown or JSON. Compatible browsers also expose native WebMCP tools to search disclosures, read this page, and discover API access.

Use the ontology-linked Cyber API with x402 pay per request, or a Y2 Pro or Elite API key with the intel:cyber scope.

Get an API key Use x402 Connect an agent

Endpoints and access details

https://api.y2.dev/api/v2/cyber/cves
https://api.y2.dev/api/v2/cyber/cves/{cveId}

A workspace owner or admin can create a Pro or Elite API key. Send Authorization: Bearer <Y2_API_KEY> from your trusted agent runtime.

For x402, omit Authorization and read the HTTP 402 payment challenge before signing a retry. Public browser tools do not make payments.

Agent access JSON · OpenAPI · CVE API guide