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.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact High

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00552.

Exploitation none

Automatable no

Technical Impact total

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
libssh2 libssh2 unaffected
Version Status Constraints
0 affected ≤ 1.11.1
7acf3dfda80c91c3a8c9f2372546301d4a1a7a8 unaffected —

No data.

No data.

No data.

Project Subscriptions

Vendors Products
Libssh2 Subscribe
Libssh2 Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8 cve-icon
https://github.com/libssh2/libssh2/pull/2052 cve-icon
https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c cve-icon
History

Thu, 18 Jun 2026 04:45:00 +0000

Type Values Removed Values Added
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.
Title libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c
First Time appeared Libssh2
Libssh2 libssh2
Weaknesses CWE-680
CPEs cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*
Vendors & Products Libssh2
Libssh2 libssh2
References
Metrics cvssV3_1

{'score': 8.1, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H'}

cvssV4_0

{'score': 9.2, 'vector': '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'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-06-18T11:46:01.897Z

Reserved: 2026-06-16T15:53:37.764Z

Link: CVE-2026-55200

cve-icon Vulnrichment

Updated: 2026-06-17T19:45:05.382Z

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses