Vulnerability in Libssh2
CVE-2026-55200
libssh2 through 1.11.1, fixed in commit 7acf3df contains an out-of-bounds write vulnerability in ssh2_transport_read() that fails to enforce upper bounds on packet_length field. Remote attackers can send crafted SSH packets with excessively large packet_length values to corrupt heap memory and achieve remote code execution.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.008 (55.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 56th percentile — 55.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.040 · newest: 0.008 · change: -0.032
Affected products
- Libssh2 — versions 0, 7acf3dfda80c91c3a8c9f2372546301d4a1a7a8, 1.11.1
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/libssh2/libssh2/pull/2052 (issue-tracking, Patch)
- github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8 (Patch, patch)
- www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-l… (Third Party Advisory, third-party-advisory)
- 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Patch)
- 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Exploit, Third Party Advisory)
Frequently asked questions
- What is CVE-2026-55200?
- CVE-2026-55200 is a high-severity vulnerability in Libssh2, classified under Integer Overflow to Buffer Overflow. CVSS score: 8.1/10. Published 2026-06-17.
- How severe is CVE-2026-55200?
- High severity. CVSS v3 base score is 8.1 out of 10.
- Is CVE-2026-55200 known to be exploited?
- 3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.