---
id: CVE-2026-66339
title: >-
  Libsoup: libsoup: proxy credentials leak to destination server via
  proxy-authorization header in connect tunnels
summary: >-
  A flaw was found in libsoup. After a CONNECT tunnel is established through an
  HTTP proxy, libsoup incorrectly attaches the Proxy-Authorization header to
  subsequent HTTPS requests sent through that tunnel to the destination server.
  This a…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N'
cvssSource: cna
cwe:
  - CWE-201
vendor: Red Hat
product: libsoup3
affected:
  - libsoup3 (all versions)
  - libsoup (all versions)
  - libsoup (all versions)
  - libsoup (all versions)
  - libsoup (all versions)
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-07-28T14:25:44.275356Z'
published: '2026-07-24'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T22:13:11.800Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-66339'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-66339'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2506951'
    label: RHBZ#2506951
tags:
  - cve.org
epss: 0.00249
epssPercentile: 0.16301
ingestedAt: '2026-11-05T23:41:31.952Z'
---

## Overview

A flaw was found in libsoup. After a CONNECT tunnel is established through an HTTP proxy, libsoup incorrectly attaches the Proxy-Authorization header to subsequent HTTPS requests sent through that tunnel to the destination server. This allows the destination server to capture proxy credentials, leading to information disclosure.

## Affected

- `libsoup3 (all versions)`
- `libsoup (all versions)`
- `libsoup (all versions)`
- `libsoup (all versions)`
- `libsoup (all versions)`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.