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.
Weakness
The product performs a calculation to determine how much memory to allocate, but an integer overflow can occur that causes less memory to be allocated than expected, leading to a buffer overflow.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Libssh2 | Libssh2 | * | 1.11.1 (including) |
| Red Hat Hardened Images | RedHat | libssh2-main-1.11.1-8.hum1 | * |
| Libssh2 | Ubuntu | devel | * |
| Libssh2 | Ubuntu | questing | * |
| Libssh2 | Ubuntu | resolute | * |
| Libssh2 | Ubuntu | upstream | * |
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/10.html
- https://cwe.mitre.org/data/definitions/100.html
- https://cwe.mitre.org/data/definitions/14.html
- https://cwe.mitre.org/data/definitions/24.html
- https://cwe.mitre.org/data/definitions/45.html
- https://cwe.mitre.org/data/definitions/46.html
- https://cwe.mitre.org/data/definitions/47.html
- https://cwe.mitre.org/data/definitions/67.html
- https://cwe.mitre.org/data/definitions/8.html
- https://cwe.mitre.org/data/definitions/9.html
- https://cwe.mitre.org/data/definitions/92.html
References
- https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8
- https://github.com/libssh2/libssh2/pull/2052
- https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c
- https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc