CVE-2026-66339

Libsoup: libsoup: proxy credentials leak to destination server via proxy-authorization header in connect tunnels

MEDIUM
6.5
CVSS Score
Published: July 24, 2026 at 11:01 PM UTC
Updated: August 24, 2026 at 05:01 PM UTC
2 products affected across 2 vendorsEnterprise LinuxLibsoup

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Severity
MEDIUM6.5
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

Description

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (2)

VDB Entryx_refsource_REDHATVendor Advisory
https://access.redhat.com/security/cve/CVE-2026-66339
Issue Trackingx_refsource_REDHATVendor AdvisoryExploitMitigation
https://bugzilla.redhat.com/show_bug.cgi?id=2506951

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.5MEDIUMredhat
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-201

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