Double Free in Libssh2
CVE-2026-66032
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.
Vulnerability class: Double Free
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.004 (38.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 38th percentile — 38.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Libssh2 — versions 0, 5e4776146552d898b9c0e1b313cd093fa8dc92d0
Weakness classification (CWE)
References
- github.com/libssh2/libssh2/pull/2180 (issue-tracking, Patch, patch, Issue Tracking)
- github.com/libssh2/libssh2/commit/5e4776146552d898b9c0e1b313cd093fa8dc92d0 (Patch, patch)
- www.vulncheck.com/advisories/libssh2-double-free-heap-corruption-via-sftp-open (Patch, Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2026-66032?
- CVE-2026-66032 is a high-severity vulnerability in Libssh2, classified under Double Free. CVSS score: 8.8/10. Published 2026-07-24.
- How severe is CVE-2026-66032?
- High severity. CVSS v3 base score is 8.8 out of 10.