CVE-2026-66034

libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1 response parser reads a server-controlled comment_len value and advances the parse pointer without verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup path frees an uninitialized pointer from a non-zeroed realloc() region.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 1.6 / Impact : 5.9

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction REQUIRED

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/libssh2/libssh2/commit/a13bb6c773f0d55ad1628cede57e99803cd898d9	Patch
https://github.com/libssh2/libssh2/pull/2202	Issue Tracking Patch
https://www.vulncheck.com/advisories/libssh2-heap-out-of-bounds-read-via-publickey-subsystem	Patch Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-07-24 17:17

Updated : 2026-07-30 15:44

NVD link : CVE-2026-66034

Mitre link : CVE-2026-66034

CVE.ORG link : CVE-2026-66034

JSON object : View

Products Affected

libssh2

libssh2

CWE

CWE-125

Out-of-bounds Read

CWE-908

Use of Uninitialized Resource

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