CVE-2026-55200

Name: CVE-2026-55200
Creator: NVD / NIST
Published: 2026-06-17T20:17:28.667+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.3/10EPSS 4.02%

Last modified Sep 17, 2026

CVE-2026-55200 is a high-severity vulnerability rated 8.3/10 on the CVSS scale. 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.. EPSS estimates a 4.02% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

8.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L

CVSS 4.0

9.2/10

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

4.02%

90.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-680

Affected Software

Vendor	Product	Versions
Libssh2	Libssh2	1.11.1

References

https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8Patch
https://github.com/libssh2/libssh2/pull/2052Patch
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, Third Party Advisory

Timeline

Published: Jun 17, 2026
Last Modified: Sep 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-55200?

How severe is CVE-2026-55200?

CVE-2026-55200 has a CVSS score of 8.3/10 (HIGH severity). The EPSS model estimates a 4.02% probability of exploitation in the next 30 days.

How do I fix CVE-2026-55200?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST