CVE-2026-66034

NameCVE-2026-66034
Descriptionlibssh2 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.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
libssh2 (PTS)bullseye1.9.0-2+deb11u1vulnerable
bookworm1.10.0-3vulnerable
trixie (security), trixie1.11.1-1+deb13u1vulnerable
forky, sid1.11.1-4vulnerable

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
libssh2source(unstable)(unfixed)

Notes

https://github.com/libssh2/libssh2/pull/2202
Fixed by: https://github.com/libssh2/libssh2/commit/a13bb6c773f0d55ad1628cede57e99803cd898d9

Search for package or bug name: Reporting problems