CVE-2026-66339

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreMEDIUM 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 — 3 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(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: 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%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
14%
KEV
Not listed

Published

July 24, 2026

Last Modified

August 24, 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.

Affected Packages

(6 across 4 ecosystems)
Debian:12(2)
PackageVulnerable rangeFixed inDependents
libsoup2.42.74.3-1 ... 2.74.3-9 (16 versions)——
libsoup33.2.2-2 ... 3.6.6-1 (35 versions)——
Debian:13(2)
PackageVulnerable rangeFixed inDependents
libsoup2.42.74.3-10.1, 2.74.3-11——
libsoup33.6.5-3 ... 3.6.6-1 (8 versions)——
Debian:11(1)
PackageVulnerable rangeFixed inDependents
libsoup2.42.72.0-2 ... 2.74.3-9 (28 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
libsoup33.6.5-3 ... 3.6.6-1 (8 versions)——

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 66× 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.

Showing the most recent 100 of 149 total refreshes for this CVE.

  1. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 08:39 UTCEG score recompute
  3. 2026-09-18 08:39 UTCGHSA enrichment
  4. 2026-09-17 09:13 UTCEG score recompute
  5. 2026-09-17 09:13 UTCGHSA enrichment
  6. 2026-09-16 14:08 UTCEPSS rescore
  7. 2026-09-16 06:38 UTCEG score recompute
  8. 2026-09-16 06:38 UTCGHSA enrichment
  9. 2026-09-16 05:15 UTCEPSS rescore
  10. 2026-09-14 16:01 UTCEG score recompute
  11. 2026-09-14 16:01 UTCGHSA enrichment
  12. 2026-09-13 15:25 UTCGHSA enrichment
  13. 2026-09-12 15:48 UTCEG score recompute
  14. 2026-09-12 15:48 UTCGHSA enrichment
  15. 2026-09-11 16:35 UTCEG score recompute
  16. 2026-09-11 16:35 UTCGHSA enrichment
  17. 2026-09-11 14:53 UTCEPSS rescore
  18. 2026-09-11 09:37 UTCEPSS rescore
  19. 2026-09-10 13:33 UTCEG score recompute
  20. 2026-09-10 13:33 UTCGHSA enrichment
  21. 2026-09-09 08:42 UTCEG score recompute
  22. 2026-09-09 08:42 UTCGHSA enrichment
  23. 2026-09-08 22:01 UTCEPSS rescore
  24. 2026-09-07 21:23 UTCEG score recompute
  25. 2026-09-07 21:23 UTCGHSA enrichment
Show 75 more
  1. 2026-09-07 16:01 UTCEPSS rescore
  2. 2026-09-06 18:35 UTCEG score recompute
  3. 2026-09-06 18:35 UTCGHSA enrichment
  4. 2026-09-06 13:47 UTCEPSS rescore
  5. 2026-09-05 19:22 UTCEG score recompute
  6. 2026-09-05 19:22 UTCGHSA enrichment
  7. 2026-09-05 15:31 UTCEPSS rescore
  8. 2026-09-04 12:44 UTCEG score recompute
  9. 2026-09-04 12:43 UTCGHSA enrichment
  10. 2026-09-04 05:07 UTCEPSS rescore
  11. 2026-09-02 14:12 UTCEPSS rescore
  12. 2026-09-01 23:15 UTCEG score recompute
  13. 2026-09-01 23:15 UTCGHSA enrichment
  14. 2026-09-01 13:54 UTCEPSS rescore
  15. 2026-09-01 04:40 UTCEPSS rescore
  16. 2026-08-30 23:26 UTCEG score recompute
  17. 2026-08-30 23:26 UTCGHSA enrichment
  18. 2026-08-30 19:17 UTCEPSS rescore
  19. 2026-08-30 00:14 UTCEG score recompute
  20. 2026-08-30 00:14 UTCGHSA enrichment
  21. 2026-08-28 21:42 UTCEPSS rescore
  22. 2026-08-27 14:46 UTCEG score recompute
  23. 2026-08-27 14:46 UTCGHSA enrichment
  24. 2026-08-26 15:30 UTCEG score recompute
  25. 2026-08-26 15:30 UTCGHSA enrichment
  26. 2026-08-26 14:47 UTCEPSS rescore
  27. 2026-08-25 16:13 UTCEG score recompute
  28. 2026-08-25 16:13 UTCGHSA enrichment
  29. 2026-08-25 13:49 UTCEPSS rescore
  30. 2026-08-24 17:01 UTCEG score recompute
  31. 2026-08-24 17:01 UTCGHSA enrichment
  32. 2026-08-23 21:46 UTCEG score recompute
  33. 2026-08-23 21:46 UTCGHSA enrichment
  34. 2026-08-23 00:19 UTCEPSS rescore
  35. 2026-08-22 22:34 UTCEG score recompute
  36. 2026-08-22 22:34 UTCGHSA enrichment
  37. 2026-08-21 23:49 UTCEPSS rescore
  38. 2026-08-21 23:21 UTCGHSA enrichment
  39. 2026-08-21 00:08 UTCEG score recompute
  40. 2026-08-21 00:08 UTCGHSA enrichment
  41. 2026-08-20 22:56 UTCEPSS rescore
  42. 2026-08-20 00:56 UTCEG score recompute
  43. 2026-08-20 00:56 UTCGHSA enrichment
  44. 2026-08-19 17:04 UTCEPSS rescore
  45. 2026-08-19 01:37 UTCEG score recompute
  46. 2026-08-19 01:37 UTCGHSA enrichment
  47. 2026-08-18 13:48 UTCEPSS rescore
  48. 2026-08-18 02:24 UTCEG score recompute
  49. 2026-08-18 02:24 UTCGHSA enrichment
  50. 2026-08-17 13:47 UTCEPSS rescore
  51. 2026-08-17 03:05 UTCEG score recompute
  52. 2026-08-17 03:05 UTCGHSA enrichment
  53. 2026-08-16 14:56 UTCEPSS rescore
  54. 2026-08-16 03:52 UTCEG score recompute
  55. 2026-08-16 03:52 UTCGHSA enrichment
  56. 2026-08-15 04:39 UTCEG score recompute
  57. 2026-08-15 04:39 UTCGHSA enrichment
  58. 2026-08-15 01:30 UTCEPSS rescore
  59. 2026-08-14 05:25 UTCEG score recompute
  60. 2026-08-14 05:25 UTCGHSA enrichment
  61. 2026-08-13 22:00 UTCEPSS rescore
  62. 2026-08-13 06:13 UTCEG score recompute
  63. 2026-08-13 06:13 UTCGHSA enrichment
  64. 2026-08-12 13:51 UTCEPSS rescore
  65. 2026-08-12 06:59 UTCEG score recompute
  66. 2026-08-12 06:59 UTCGHSA enrichment
  67. 2026-08-11 07:46 UTCEG score recompute
  68. 2026-08-11 07:46 UTCGHSA enrichment
  69. 2026-08-11 00:00 UTCEPSS rescore
  70. 2026-08-10 08:33 UTCEG score recompute
  71. 2026-08-10 08:33 UTCGHSA enrichment
  72. 2026-08-09 13:47 UTCEPSS rescore
  73. 2026-08-09 09:20 UTCEG score recompute
  74. 2026-08-09 09:20 UTCGHSA enrichment
  75. 2026-08-08 16:37 UTCEPSS rescore

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 August 24, 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 86.3% 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

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