CVE-2026-55200
libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c
CVSS Score
8.1
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-680 |
| Vendor | libssh2 |
| Product | libssh2 |
| Published | Jun 17, 2026 |
| Last Updated | Jul 14, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Affected Versions
libssh2 / libssh2
0 ≤ 1.11.1
References
github.com: https://github.com/libssh2/libssh2/pull/2052 github.com: https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8 vulncheck.com: https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c web.archive.org: https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc
Credits
Tristan Madani (@TristanInSec)