What is CVE-2026-66035?

CVE-2026-66035 is a high-severity vulnerability in Libssh2, classified under Heap-based Buffer Overflow. CVSS score: 7.5/10. Published 2026-07-24.

How severe is CVE-2026-66035?

High severity. CVSS v3 base score is 7.5 out of 10.

Buffer overflow in Libssh2

CVE-2026-66035

libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packet_length…

Vulnerability class: Buffer Overflow

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.

Affected products

Libssh2 — versions 0, 42e33d81577ed4b95d4b4f6f845e5ee8efe5eeb4

Weakness classification (CWE)

CWE-122 — Heap-based Buffer Overflow

References

disclosure@vulncheck.com (issue-tracking, patch)
disclosure@vulncheck.com (patch)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-66035?: CVE-2026-66035 is a high-severity vulnerability in Libssh2, classified under Heap-based Buffer Overflow. CVSS score: 7.5/10. Published 2026-07-24.
How severe is CVE-2026-66035?: High severity. CVSS v3 base score is 7.5 out of 10.