CVE-2026-8958

HIGHNVD 8.68.6—
EchelonGraph scoreMEDIUM confidence

Score 8.6 from GitHub Security Advisory (severity: HIGH) published 2026-05-19. NVD baseline CVSS 8.6; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
8.6EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.6Exploit: None knownExposed: 0

A fix is available — apply it.

Information disclosure, sandbox escape in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

CVSS v3
8.6
EG Score
8.6(medium)
EG Risk
54(Track)
EG Risk 54/100SSVC: 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
Severity86% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
28%
KEV
Not listed

Published

May 19, 2026

Last Modified

May 20, 2026

Advisory Details (3)

Auto-updated May 19, 2026
No patch confirmed yet.
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

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2034713

Vendor Advisories for CVE-2026-8958(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 / EcosystemFixed in / PatchReleasedSource
redhatfirefox-0:140.11.0-1.el10_02026-06-22redhat
redhatthunderbird-0:140.11.0-1.el10_02026-06-17redhat
redhatfirefox-0:140.11.0-1.el9_22026-06-17redhat
redhatfirefox-0:140.11.0-1.el9_42026-06-17redhat
redhatfirefox-0:140.11.0-1.el9_62026-06-17redhat
redhatthunderbird-0:140.11.0-1.el9_62026-06-17redhat
redhatfirefox-0:140.11.0-1.el8_82026-06-17redhat
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_42026-06-17redhat
redhatthunderbird-0:140.11.0-1.el8_62026-06-17redhat
redhatthunderbird-0:140.11.0-1.el8_82026-06-16redhat
redhatthunderbird-0:140.11.0-1.el8_42026-06-16redhat
redhatthunderbird-0:140.11.0-1.el9_42026-06-16redhat
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
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
redhatthunderbird-0:140.11.0-1.el9_82026-05-27redhat

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 rangeFixed inDependents
firefox-esr102.1.0esr-1 ... 91.9.1esr-1~deb9u1 (275 versions)140.11.0esr-1~deb11u1—
thunderbird1:102.0.1-1 ... 1:91.9.0-1~deb9u1 (326 versions)1:140.11.0esr-1~deb11u1—
Debian:12(2)
PackageVulnerable rangeFixed inDependents
firefox-esr102.11.0esr-1 ... 140.9.1esr-1~deb13u1 (182 versions)140.11.0esr-1~deb12u1—
thunderbird1:102.11.0-1 ... 1:140.9.1esr-1~deb13u1 (211 versions)1:140.11.0esr-1~deb12u1—
Debian:13(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (58 versions)140.11.0esr-1~deb13u1—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (67 versions)1:140.11.0esr-1~deb13u1—
Debian:14(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (59 versions)140.11.0esr-1—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (68 versions)1:140.11.0esr-1—

Weakness Classification(2)

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 7× in last 7d / 41× 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 267 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-8958?
CVE-2026-8958 is a high vulnerability published on May 19, 2026. Information disclosure, sandbox escape in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.
When was CVE-2026-8958 disclosed?
CVE-2026-8958 was first published in the National Vulnerability Database 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-2026-8958 actively exploited?
CVE-2026-8958 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 72.4% of all scored CVEs.
What is the CVSS score of CVE-2026-8958?
CVE-2026-8958 has a CVSS v3 base score of 8.6 (NVD).
How do I remediate CVE-2026-8958?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-8958, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-8958

Explore →

Is Your Infrastructure Affected by CVE-2026-8958?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs