CVE-2026-55200

libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c

State: Published
Severity: 9.2 Critical
Published: Jun 17, 2026
Updated: Oct 22, 2026
Reserved: Jun 16, 2026

Description

libssh2 1.11.1, fixed in commit 97acf3d, 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.

Scores

CVSS	Score	Vector	Source
4.0	9.2 Critical	CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N	VulnCheck
3.1	8.1 High	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H	VulnCheck

Weaknesses

CWE-680 Integer Overflow to Buffer Overflow

Affected Products

Product	Versions
libssh2libssh2	1.11.1Affected 1c3f1b7da588f2652260285529ec3c1f1125eb4e to before 97acf3dfda80c91c3a8c9f2372546301d4a1a7a8Affected

References

Pull Requestissue-tracking
Patch Commitpatch
https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-cthird-party-advisory
https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-pocexploit

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