CVE-2026-55200

Published Jun 17, 2026

Last updated a month ago

CVSS critical 9.2

SSH

Curl

Tunneling protocol

Port (22)

Overview

AI description

Automated description summarized from trusted sources.

CVE-2026-55200 describes an out-of-bounds write vulnerability found in libssh2 versions up to and including 1.11.1. The flaw resides within the `ssh2_transport_read()` function, which fails to properly enforce upper bounds on the `packet_length` field during the reading of incoming SSH packets. This oversight allows remote attackers to send specially crafted SSH packets containing excessively large `packet_length` values. By exploiting this vulnerability, an attacker can corrupt heap memory, potentially leading to remote code execution on affected systems. The issue was addressed in commit 7acf3df of the libssh2 project.

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.
Source: disclosure@vulncheck.com
NVD status: Analyzed
Products: libssh2

Risk scores

CVSS 4.0

Type: Secondary
Base score: 9.2
Impact score: -
Exploitability score: -
Vector string: 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
Severity: CRITICAL

CVSS 3.1

Type: Primary
Base score: 8.3
Impact score: 5.5
Exploitability score: 2.8
Vector string: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L
Severity: HIGH

Weaknesses

disclosure@vulncheck.com: CWE-680

Hype score: Not currently trending

Configurations

[
  {
    "nodes": [
      {
        "cpeMatch": [
          {
            "criteria": "cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*",
            "matchCriteriaId": "00D62356-F677-41CF-AC66-2871AD2112BA",
            "versionEndIncluding": "1.11.1",
            "vulnerable": true
          }
        ],
        "negate": false,
        "operator": "OR"
      }
    ]
  }
]

References

Sources include official advisories and independent security research.