Critical · CVSS 9.2CVE-2026-55200

libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.cCVE-2026-55200

Answer in brief

CVE-2026-55200 records a Critical severity (CVSS 9.2) vulnerability in libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c. The current sources do not mark it as known exploited. The current feed maps libssh2/libssh2 (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jun 17, 2026Updated Oct 22, 2026Source checked Oct 22, 2026First seen by HOL Jun 22, 2026Material review Oct 22, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.2
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 9.2. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps libssh2/libssh2 (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:a:libssh2:libssh2:1.11.1:::::::*	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
libssh2/libssh2generic	1.11.1 \|\| >=1c3f1b7da588f2652260285529ec3c1f1125eb4e <97acf3dfda80c91c3a8c9f2372546301d4a1a7a8	97acf3dfda80c91c3a8c9f2372546301d4a1a7a8

Recommended response

Check inventory. Check lockfiles and deployed manifests for libssh2/libssh2.
Review the reported fix. Update libssh2/libssh2 to 97acf3dfda80c91c3a8c9f2372546301d4a1a7a8 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jun 17, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 22, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jun 22, 2026

Sources and claim methodology

Upstream source description

libssh2 1.11.1, fixed in commit 97acf3d, 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.

Quoted source text, attributed separately from HOL analysis.