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Linux Distros Unpatched Vulnerability : CVE-2026-15806

medium Nessus Plugin ID 338038

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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.

 - The HTTPPasswordMgr class in the urllib.request module, along with its subclasses HTTPPasswordMgrWithDefaultRealm and HTTPPasswordMgrWithPriorAuth, did not take the URL scheme into account when matching stored credentials against a requested URL. Credentials added for an https:// URL were also used for requests to the same host over http://, so an attacker able to redirect or downgrade a client to plain HTTP (for example, via an HTTPS-to-HTTP redirect or an on-path position) could capture credentials in cleartext. Credentials added for http:// URLs could likewise be sent over https://. Credential matching is now scoped by URL scheme. Credentials registered with a URL that includes a scheme are only used for requests with the same scheme. Credentials registered with a bare authority (such as example.com or example.com:8080) continue to match any scheme, preserving compatibility with existing code, including proxy authentication. Users who cannot upgrade immediately can mitigate by ensuring that applications never make plain http:// requests to hosts for which credentials are registered, for example by not following redirects to http:// URLs. (CVE-2026-15806)

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

Solution

There is no known solution at this time.

See Also

https://security-tracker.debian.org/tracker/CVE-2026-15806

https://ubuntu.com/security/CVE-2026-15806

Plugin Details

Severity: Medium

ID: 338038

File Name: unpatched_CVE_2026_15806.nasl

Version: 1.2

Type: Local

Agent: unix

Family: Misc.

Published: 8/19/2026

Updated: 8/19/2026

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Azure, Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3.9

Percentile: 52.57

CVSS v2

Risk Factor: Medium

Base Score: 4.3

Temporal Score: 3.7

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

CVSS Score Source: CVE-2026-15806

CVSS v3

Risk Factor: Medium

Base Score: 6.9

Temporal Score: 6.3

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

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

CVSS v4

Risk Factor: Medium

Base Score: 6

Threat Score: 2.3

Threat Vector: CVSS:4.0/E:U

Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:14.04:-:lts, cpe:/o:canonical:ubuntu_linux:16.04:-:lts, cpe:/o:canonical:ubuntu_linux:18.04:-:lts, cpe:/o:canonical:ubuntu_linux:20.04:-:lts, cpe:/o:canonical:ubuntu_linux:22.04:-:lts, cpe:/o:canonical:ubuntu_linux:24.04:-:lts, cpe:/o:canonical:ubuntu_linux:26.04:-:lts, cpe:/o:debian:debian_linux:11.0, cpe:/o:debian:debian_linux:12.0, cpe:/o:debian:debian_linux:13.0, cpe:/o:debian:debian_linux:14.0, p-cpe:/a:canonical:ubuntu_linux:python2.7, p-cpe:/a:canonical:ubuntu_linux:python3.10, p-cpe:/a:canonical:ubuntu_linux:python3.11, p-cpe:/a:canonical:ubuntu_linux:python3.12, p-cpe:/a:canonical:ubuntu_linux:python3.14, p-cpe:/a:canonical:ubuntu_linux:python3.4, p-cpe:/a:canonical:ubuntu_linux:python3.5, p-cpe:/a:canonical:ubuntu_linux:python3.6, p-cpe:/a:canonical:ubuntu_linux:python3.7, p-cpe:/a:canonical:ubuntu_linux:python3.8, p-cpe:/a:canonical:ubuntu_linux:python3.9, p-cpe:/a:debian:debian_linux:pypy3, p-cpe:/a:debian:debian_linux:python2.7, p-cpe:/a:debian:debian_linux:python3.11, p-cpe:/a:debian:debian_linux:python3.13, p-cpe:/a:debian:debian_linux:python3.14, p-cpe:/a:debian:debian_linux:python3.15, p-cpe:/a:debian:debian_linux:python3.9

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

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 8/18/2026

Reference Information

CVE: CVE-2026-15806