Detections
Analytics

Ubuntu 24.04 LTS / 25.10 / 26.04 LTS : libssh2 vulnerabilities (USN-8486-1)

critical Nessus Plugin ID 325003

Synopsis

The remote Ubuntu host is missing one or more security updates.

Description

The remote Ubuntu 24.04 LTS / 25.10 / 26.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8486-1 advisory.

 It was discovered that libssh2 incorrectly handled the sftp_symlink() function. A malicious SSH server or machine-in-the-middle attacker could possibly use this issue to obtain sensitive information or cause a denial of service. (CVE-2025-15661)

 It was discovered that libssh2 had a pre-authentication denial of service vulnerability in the SSH_MSG_EXT_INFO handler. A malicious SSH server could possibly use this issue to cause a client CPU exhaustion loop, resulting in a denial of service. (CVE-2026-55199)

 It was discovered that libssh2 incorrectly handled packet length fields. A remote attacker could possibly use this issue to execute arbitrary code. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS.
 (CVE-2026-55200)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Update the affected libssh2-1-dev and / or libssh2-1t64 packages.

See Also

https://ubuntu.com/security/notices/USN-8486-1

Plugin Details

Severity: Critical

ID: 325003

File Name: ubuntu_USN-8486-1.nasl

Version: 1.1

Type: Local

Agent: unix

Published: 7/3/2026

Updated: 7/3/2026

Supported Sensors: Continuous Assessment, Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: High

Score: 8.8

Percentile: 99.7

CVSS v2

Risk Factor: High

Base Score: 9.7

Temporal Score: 7.6

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:P

CVSS Score Source: CVE-2026-55200

CVSS v3

Risk Factor: High

Base Score: 8.3

Temporal Score: 7.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

CVSS v4

Risk Factor: Critical

Base Score: 9.2

Threat Score: 8.2

Threat Vector: CVSS:4.0/E:P

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

Vulnerability Information

CPE: p-cpe:/a:canonical:ubuntu_linux:libssh2-1t64, cpe:/o:canonical:ubuntu_linux:25.10, p-cpe:/a:canonical:ubuntu_linux:libssh2-1-dev, cpe:/o:canonical:ubuntu_linux:24.04:-:lts, cpe:/o:canonical:ubuntu_linux:26.04:-:lts

Required KB Items: Host/cpu, Host/Ubuntu, Host/Ubuntu/release, Host/Debian/dpkg-l

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 6/30/2026

Vulnerability Publication Date: 6/17/2026

Reference Information

CVE: CVE-2025-15661, CVE-2026-55199, CVE-2026-55200

USN: 8486-1