Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-66339

CVE-2026-66339MEDIUM

Red Hat Red Hat Enterprise Linux 10 — Libsoup: libsoup: proxy credentials leak to destination server via proxy-authorization header in connect tunnels

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   R  U  H  N  N    6.5   .0025   14.7     —

AFFECTED
  Product                      Versions     Fixed
  Red Hat Enterprise Linux 10  unspecified  —
  Red Hat Enterprise Linux 6   unspecified  —
  Red Hat Enterprise Linux 7   unspecified  —
  Red Hat Enterprise Linux 8   unspecified  —
  Red Hat Enterprise Linux 9   unspecified  —

TIMELINE
  Jul 24  Reserved by redhat
  Jul 24  Published (CNA: redhat)
  Aug 24  EXPLOIT PUBLISHED — CVE-2026-66339 (Red Hat Enterprise Linux 10). Public exploit reference added.

CWE-201 · CNA: redhat · CVSS v3.1 · 2 references · NVD status: Analyzed

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
July 24, 2026	Reserved	Reserved by redhat
July 24, 2026	Published	Published (CNA: redhat)
August 24, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-66339 (Red Hat Enterprise Linux 10). Public exploit reference added.

Affected

Affected products and packages — 5 rows
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
Red Hat	Red Hat Enterprise Linux 10	—	—	—
Red Hat	Red Hat Enterprise Linux 6	—	—	—
Red Hat	Red Hat Enterprise Linux 7	—	—	—
Red Hat	Red Hat Enterprise Linux 8	—	—	—
Red Hat	Red Hat Enterprise Linux 9	—	—	—

Weaknesses

CWE-201

References (2)

https://access.redhat.com/security/cve/CVE-2026-66339 [Vendor Advisory]
https://bugzilla.redhat.com/show_bug.cgi?id=2506951 [Issue Tracking, Vendor Advisory, Exploit, Mitigation]

Authoritative record: CVE-2026-66339 at cve.org

Vendors: red hat

Weaknesses: CWE-201

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-66339 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.