CVE-2026-5731

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-04-07. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.8Exploit: None knownExposed: 0

A fix is available — apply it.

Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 149.0.2, Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
44(Track)
EG Risk 44/100SSVC: 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
Severity98% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
27%
KEV
Not listed

Published

April 7, 2026

Last Modified

July 15, 2026

Advisory Details (10)

Auto-updated Sep 12, 2026
Patch available. Sources: redhat.
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.6 Extended Update Support.

https://access.redhat.com/errata/RHSA-2026:13342
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions.

https://access.redhat.com/errata/RHSA-2026:12264
redhat Patch Available

Affected: Red Hat Enterprise Linux 10.0 Extended Update Support.

https://access.redhat.com/errata/RHSA-2026:11813
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.2 Advanced Update Support.

https://access.redhat.com/errata/RHSA-2026:11805
generic

Security Vulnerabilities fixed in Thunderbird 140.9.1 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-29/
generic

Security Vulnerabilities fixed in Thunderbird 149.0.2 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-28/
generic

Security Vulnerabilities fixed in Firefox ESR 140.9.1 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-27/
generic

Security Vulnerabilities fixed in Firefox ESR 115.34.1 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-26/
generic

Security Vulnerabilities fixed in Firefox 149.0.2 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-25/
generic

Client Challenge

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2021894%2C2022225%2C2022252%2C2022294%2C2023007%2C2023130%2C2023191%2C2023364%2C2023829%2C2024074%2C2024417%2C2024433%2C2024436%2C2024437%2C2024453%2C2024461%2C2024462%2C2024472%2C2024474%2C2024477%2C2025364%2C2025401%2C2025402%2C2025472%2C2026287%2C2026299%2C2026305%2C2026426

Vendor Advisories for CVE-2026-5731(20)

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

Patch Availability(24)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatthunderbird-0:140.9.1-1.el8_62026-05-11redhat
redhatfirefox-0:140.9.1-2.el7_92026-05-06redhat
redhatfirefox-0:140.9.1-1.el9_22026-05-06redhat
redhatthunderbird-0:140.9.1-1.el8_42026-05-06redhat
redhatthunderbird-0:140.9.1-1.el8_82026-05-06redhat
redhatfirefox-0:140.9.1-1.el9_02026-05-05redhat
redhatfirefox-0:140.9.1-1.el8_82026-05-05redhat
redhatfirefox-0:140.9.1-1.el9_62026-05-05redhat
redhatfirefox-0:140.9.1-1.el8_42026-05-05redhat
redhatfirefox-0:140.9.1-1.el9_42026-05-05redhat
redhatfirefox-0:140.9.1-1.el10_02026-05-05redhat
redhatfirefox-0:140.9.1-1.el8_62026-05-05redhat
redhatthunderbird-0:140.9.1-1.el9_62026-05-04redhat
redhatthunderbird-0:140.9.1-1.el9_22026-05-04redhat
redhatthunderbird-0:140.9.1-1.el9_42026-05-04redhat
redhatthunderbird-0:140.9.1-1.el9_02026-04-30redhat
redhatthunderbird-0:140.9.1-1.el10_02026-04-29redhat
redhatfirefox-0:140.9.1-1.el8_22026-04-29redhat
redhatthunderbird-0:140.9.1-1.el10_12026-04-22redhat
redhatthunderbird-0:140.9.1-1.el8_102026-04-21redhat
redhatthunderbird-0:140.9.1-1.el9_72026-04-16redhat
redhatfirefox-0:140.9.1-1.el8_102026-04-14redhat
redhatfirefox-0:140.9.1-1.el9_72026-04-13redhat
redhatfirefox-0:140.9.1-1.el10_12026-04-13redhat

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 (259 versions)140.9.1esr-1~deb11u1—
thunderbird1:102.0.1-1 ... 1:91.9.0-1~deb9u1 (310 versions)1:140.9.1esr-1~deb11u1—
Debian:12(2)
PackageVulnerable rangeFixed inDependents
firefox-esr102.11.0esr-1 ... 140.9.1esr-1~deb11u1 (166 versions)140.9.1esr-1~deb12u1—
thunderbird1:102.11.0-1 ... 1:140.9.1esr-1~deb11u1 (195 versions)1:140.9.1esr-1~deb12u1—
Debian:13(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb12u1 (42 versions)140.9.1esr-1~deb13u1—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb12u1 (51 versions)1:140.9.1esr-1~deb13u1—
Debian:14(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (43 versions)140.9.1esr-1—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (52 versions)1:140.9.1esr-1—

Weakness Classification(2)

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

Additional Vendor Advisories

(4)

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 5× in last 7d / 25× 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 287 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-5731?
CVE-2026-5731 is a critical vulnerability published on April 7, 2026. Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code.…
When was CVE-2026-5731 disclosed?
CVE-2026-5731 was first published in the National Vulnerability Database on April 7, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-5731 actively exploited?
CVE-2026-5731 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 72.9% of all scored CVEs.
What is the CVSS score of CVE-2026-5731?
CVE-2026-5731 has a CVSS v3.1 base score of 9.8 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-5731?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-5731, 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-2026-5731

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