Vulnerability Description
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 Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Libssh2 | Libssh2 | <= 1.11.1 |
Related Weaknesses (CWE)
References
- https://github.com/libssh2/libssh2/commit/a13bb6c773f0d55ad1628cede57e99803cd898Patch
- https://github.com/libssh2/libssh2/pull/2202Issue TrackingPatch
- https://www.vulncheck.com/advisories/libssh2-heap-out-of-bounds-read-via-publickPatchThird Party Advisory
FAQ
What is CVE-2026-66034?
CVE-2026-66034 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 a...
How severe is CVE-2026-66034?
CVE-2026-66034 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-66034?
Check the references section above for vendor advisories and patch information. Affected products include: Libssh2 Libssh2.