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Linux Distros Unpatched Vulnerability : CVE-2026-121623

high Nessus Plugin ID 377472

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 Symfony Serializer component DataUriNormalizer::denormalize() matches the data: scheme with a case- sensitive regular expression, allowing a value with an uppercase scheme, such as DATA:,/../../../etc/passwd, to bypass it, resulting in Arbitrary Local File Read through Path Traversal in Symfony versions prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11. A value whose scheme is not lowercase data: are treated as a local file path and opened instead of being decoded as inline data, so the resulting File, \SplFileInfo, or \SplFileObject points at a file on the server, which the application then handles as the uploaded content. Any endpoint that deserializes untrusted input into one of these types is affected. FrameworkBundle registers DataUriNormalizer ahead of ObjectNormalizer by default. A single request with a crafted DATA: value is enough to read arbitrary local files that the application can access, with no authentication needed if the endpoint is public.
 (CVE-2026-121623)

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-2026-121623

Plugin Details

Severity: High

ID: 377472

File Name: unpatched_CVE_2026_121623.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Misc.

Published: 11/7/2026

Updated: 11/7/2026

Supported Sensors: Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3

Percentile: 23.84

CVSS v2

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.4

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

CVSS Score Source: CVE-2026-121623

CVSS v3

Risk Factor: Critical

Base Score: 9.8

Temporal Score: 9

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

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

CVSS v4

Risk Factor: High

Base Score: 8.2

Threat Score: 4.6

Threat Vector: CVSS:4.0/E:U

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

Vulnerability Information

CPE: cpe:/o:debian:debian_linux:12.0, cpe:/o:debian:debian_linux:13.0, cpe:/o:debian:debian_linux:14.0, p-cpe:/a:debian:debian_linux:symfony

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: 11/6/2026

Reference Information

CVE: CVE-2026-121623