CVE-2026-55200

libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c

HIGH
8.3
CVSS Score
Published: June 17, 2026 at 07:03 PM UTC
Updated: October 22, 2026 at 07:17 PM UTC
1 product affected across 1 vendorLIBSSH2

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Severity
HIGH8.3
Exploit prediction
EPSS 4%
SSVC
PoC

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Vendor states this is fixed in 7acf3dfda80c91c3a8c9f2372546301d4a1a7a8 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCPoCNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
LOW
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-680

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