Linux Distros Unpatched Vulnerability : CVE-2026-55599

medium Nessus Plugin ID 322228

Synopsis

The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be patched.

Description

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

- phpseclib is a PHP secure communications library. From 0.1.1 until 1.0.30, 2.0.55, and 3.0.54, when an application validates an untrusted X.509 certificate with phpseclib, X509::validateSignature() reads a URL out of that certificate's Authority Information Access (AIA) extension and connects to it. Attacker who supplies certificate fully controls host, port, and path of that connection. URL fetching is enabled by default, and no destination is blocked. An unauthenticated attacker can therefore make a validating server open connections to internal hosts and ports it should never reach, for example loopback 127.0.0.1, cloud metadata address 169.254.169.254, and internal-only services. This is a server-side request forgery (SSRF) caused by an insecure default. This vulnerability is fixed in 1.0.30, 2.0.55, and 3.0.54. (CVE-2026-55599)

Note that Nessus relies on the presence of the package as reported by the vendor.

Solution

There is no known solution at this time.

Plugin Details

Severity: Medium

ID: 322228

File Name: unpatched_CVE_2026_55599.nasl

Version: 1.2

Type: Local

Agent: unix

Family: Misc.

Published: 6/23/2026

Updated: 6/24/2026

Supported Sensors: Agentless Assessment, Frictionless Assessment Agent, Frictionless Assessment AWS, Frictionless Assessment Azure, Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: Low

Score: 2.4

CVSS v3

Risk Factor: Medium

Base Score: 5.8

Temporal Score: 5.3

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

Temporal Vector: CVSS:3.0/E:U/RL:U/RC:C

CVSS Score Source: CVE-2026-55599

Vulnerability Information

CPE: cpe:/o:debian:debian_linux:11.0, p-cpe:/a:canonical:ubuntu_linux:phpseclib, cpe:/o:canonical:ubuntu_linux:20.04:-:lts, cpe:/o:canonical:ubuntu_linux:25.10, cpe:/o:canonical:ubuntu_linux:24.04:-:lts, cpe:/o:canonical:ubuntu_linux:16.04:-:lts, p-cpe:/a:debian:debian_linux:php-phpseclib, cpe:/o:canonical:ubuntu_linux:18.04:-:lts, p-cpe:/a:debian:debian_linux:phpseclib, cpe:/o:debian:debian_linux:13.0, cpe:/o:canonical:ubuntu_linux:22.04:-:lts, p-cpe:/a:debian:debian_linux:php-phpseclib3, cpe:/o:debian:debian_linux:12.0, cpe:/o:canonical:ubuntu_linux:26.04:-:lts

Required KB Items: Host/cpu, Host/local_checks_enabled, global_settings/vendor_unpatched, Host/OS/identifier

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 6/22/2026

Reference Information

CVE: CVE-2026-55599

Detections

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