CVE-2026-8950

CRITICALNVD 9.39.3—
EchelonGraph scoreMEDIUM confidence

Score 9.3 from GitHub Security Advisory (severity: CRITICAL) published 2026-05-19. NVD baseline CVSS 9.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
9.3EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 9.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Same-origin policy bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

CVSS v3
9.3
EG Score
9.3CRITICALmedium confidence
EG Risk
42
EG Risk 42/100

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
Severity93% × 45%
Exploitation0% × 40%
Automatability0% × 15%
EPSS PROB
0.2%
EPSS %ILE
10th
KEV
Not listed

Published

May 19, 2026

Last Modified

May 20, 2026

Advisory Details (5)

Auto-updated Sep 23, 2026
🔬 Proof of concept available. Patch available.
generic

Security Vulnerabilities fixed in Thunderbird 140.11 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-51/
generic

Security Vulnerabilities fixed in Thunderbird 151 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-50/
generic

Security Vulnerabilities fixed in Firefox ESR 140.11 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-48/
generic

Security Vulnerabilities fixed in Firefox 151 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-46/
generic🟡 PoC Available

1965430 - (CVE-2026-8950) Form POST requests do not set Origin header to null after redirect

https://bugzilla.mozilla.org/show_bug.cgi?id=1965430

Vendor Advisories for CVE-2026-8950(20)

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

Patch Availability(21)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatfirefox-0:140.11.0-1.el10_02026-06-22redhat
redhatfirefox-0:140.11.0-1.el8_62026-06-17redhat
redhatfirefox-0:140.11.0-1.el7_92026-06-17redhat
redhatfirefox-0:140.11.0-1.el8_82026-06-17redhat
redhatthunderbird-0:140.11.0-1.el8_62026-06-17redhat
redhatfirefox-0:140.11.0-1.el8_42026-06-17redhat
redhatthunderbird-0:140.11.0-1.el9_62026-06-17redhat
redhatfirefox-0:140.11.0-1.el9_62026-06-17redhat
redhatfirefox-0:140.11.0-1.el9_22026-06-17redhat
redhatfirefox-0:140.11.0-1.el9_42026-06-17redhat
redhatthunderbird-0:140.11.0-1.el10_02026-06-17redhat
redhatthunderbird-0:140.11.0-1.el9_42026-06-16redhat
redhatthunderbird-0:140.11.0-1.el8_42026-06-16redhat
redhatthunderbird-0:140.11.0-1.el8_82026-06-16redhat
redhatthunderbird-0:140.11.0-1.el9_22026-06-16redhat
redhatthunderbird-0:140.11.0-1.el8_102026-06-03redhat
redhatthunderbird-0:140.11.0-1.el10_22026-06-01redhat
redhatthunderbird-0:140.11.0-1.el9_82026-05-27redhat
redhatfirefox-0:140.11.0-1.el9_82026-05-27redhat
redhatfirefox-0:140.11.0-1.el8_102026-05-27redhat
redhatfirefox-0:140.11.0-1.el10_22026-05-27redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(8 across 4 ecosystems)
Debian:11(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr102.1.0esr-1 ... 91.9.1esr-1~deb9u1 (275 versions)
  • every version up to 140.11.0esr-1~deb11u1: fixed in 140.11.0esr-1~deb11u1
—
thunderbird1:102.0.1-1 ... 1:91.9.0-1~deb9u1 (326 versions)
  • every version up to 1:140.11.0esr-1~deb11u1: fixed in 1:140.11.0esr-1~deb11u1
—
Debian:12(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr102.11.0esr-1 ... 140.9.1esr-1~deb13u1 (182 versions)
  • every version up to 140.11.0esr-1~deb12u1: fixed in 140.11.0esr-1~deb12u1
—
thunderbird1:102.11.0-1 ... 1:140.9.1esr-1~deb13u1 (211 versions)
  • every version up to 1:140.11.0esr-1~deb12u1: fixed in 1:140.11.0esr-1~deb12u1
—
Debian:13(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (58 versions)
  • every version up to 140.11.0esr-1~deb13u1: fixed in 140.11.0esr-1~deb13u1
—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (67 versions)
  • every version up to 1:140.11.0esr-1~deb13u1: fixed in 1:140.11.0esr-1~deb13u1
—
Debian:14(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (59 versions)
  • every version up to 140.11.0esr-1: fixed in 140.11.0esr-1
—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (68 versions)
  • every version up to 1:140.11.0esr-1: fixed in 1:140.11.0esr-1
—

Weakness Classification(1)

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

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 6× in last 7d / 27× 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 488 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-8950?
CVE-2026-8950 is a critical vulnerability published on May 19, 2026. Same-origin policy bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.
When was CVE-2026-8950 disclosed?
CVE-2026-8950 was first published on May 19, 2026, with the most recent update on May 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-8950 actively exploited?
CVE-2026-8950 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (10th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-8950?
CVE-2026-8950 has a CVSS v3 base score of 9.3 (NVD).
How do I remediate CVE-2026-8950?
A fix for CVE-2026-8950 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-8950 are linked in the Vendor Advisories panel on this page.

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