# CVE-2026-55200

## Summary

- **CVE ID:** CVE-2026-55200
- **Severity:** CRITICAL
- **CVSS Score:** 9.2 (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)
- **CWE:** CWE-680
- **Published:** Jun 17, 2026
- **Last Modified:** Jul 14, 2026

## Description

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.

## Affected Products

- libssh2 — libssh2 (0)
- libssh2 — libssh2 (7acf3dfda80c91c3a8c9f2372546301d4a1a7a8)

## References

- [CNA](https://github.com/libssh2/libssh2/pull/2052)
- [CNA](https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8)
- [CNA](https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c)
- [CISA-ADP](https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc)
- [CISA-ADP](https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 4.02%
- **EPSS Percentile:** 90.0

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._