CVE-2026-66339

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreHIGH confidence

Score 6.5 from GitHub Security Advisory published 2026-07-25. a secondary CVSS source baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
6.5
EG Score
6.5(high)
EG Risk
34(Track)
EG Risk 34/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity65% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
14%
KEV
Not listed

Published

July 24, 2026

Last Modified

July 27, 2026

Advisory Details (2)

Auto-updated Jul 25, 2026
Patch available. Sources: redhat.
redhat

2506951 – (CVE-2026-66339) CVE-2026-66339 libsoup: libsoup: Proxy credentials leak to destination server via Proxy-Authorization header in CONNECT tunnels

https://bugzilla.redhat.com/show_bug.cgi?id=2506951
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-66339

Vendor Advisories for CVE-2026-66339(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 13× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-27 20:43 UTCEG score recompute
  2. 2026-07-27 20:43 UTCGHSA enrichment
  3. 2026-07-27 14:14 UTCEPSS rescore
  4. 2026-07-27 08:55 UTCEG score recompute
  5. 2026-07-27 08:55 UTCGHSA enrichment
  6. 2026-07-26 14:54 UTCEPSS rescore
  7. 2026-07-26 14:54 UTCEPSS rescore
  8. 2026-07-26 09:43 UTCEG score recompute
  9. 2026-07-26 09:43 UTCGHSA enrichment
  10. 2026-07-25 14:18 UTCEPSS rescore
  11. 2026-07-25 14:18 UTCEPSS rescore
  12. 2026-07-24 23:17 UTCEG score recompute
  13. 2026-07-24 23:16 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-66339?
CVE-2026-66339 is a medium vulnerability published on July 24, 2026. 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,…
When was CVE-2026-66339 disclosed?
CVE-2026-66339 was first published in the National Vulnerability Database on July 24, 2026, with the most recent update on July 27, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66339 actively exploited?
CVE-2026-66339 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 86.2% of all scored CVEs.
What is the CVSS score of CVE-2026-66339?
CVE-2026-66339 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-66339?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66339, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-66339

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