CVE-2026-4720

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-03-24. 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 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. 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, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

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
36%
KEV
Not listed

Published

March 24, 2026

Last Modified

July 15, 2026

Advisory Details (10)

Auto-updated Aug 29, 2026
Patch available. Sources: redhat.
redhat Patch Available

Affected: Red Hat Enterprise Linux 10.

https://access.redhat.com/errata/RHSA-2026:6342
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.

https://access.redhat.com/errata/RHSA-2026:6188
redhat Patch Available

Affected: Red Hat Enterprise Linux 8.

https://access.redhat.com/errata/RHSA-2026:5932
redhat Patch Available

Affected: Red Hat Enterprise Linux 10.

https://access.redhat.com/errata/RHSA-2026:5931
redhat Patch Available

Affected: Red Hat Enterprise Linux 9.

https://access.redhat.com/errata/RHSA-2026:5930
generic

Security Vulnerabilities fixed in Thunderbird 140.9 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-24/
generic

Security Vulnerabilities fixed in Thunderbird 149 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-23/
generic

Security Vulnerabilities fixed in Firefox ESR 140.9 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-22/
generic

Security Vulnerabilities fixed in Firefox 149 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-20/
generic

Client Challenge

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2004652%2C2019372%2C2021922%2C2022567%2C2022733

Vendor Advisories for CVE-2026-4720(20)

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

Patch Availability(25)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatthunderbird-0:140.9.0-1.el8_42026-04-20redhat
redhatfirefox-0:140.9.0-1.el7_92026-04-16redhat
redhatthunderbird-0:140.9.0-1.el8_82026-04-15redhat
redhatthunderbird-0:140.9.0-1.el9_02026-04-15redhat
redhatthunderbird-0:140.9.0-1.el9_22026-04-15redhat
redhatthunderbird-0:140.9.0-1.el8_22026-04-15redhat
redhatthunderbird-0:140.9.0-1.el9_42026-04-15redhat
redhatthunderbird-0:140.9.0-1.el10_02026-04-15redhat
redhatthunderbird-0:140.9.0-1.el8_62026-04-15redhat
redhatthunderbird-0:140.9.0-1.el9_62026-04-15redhat
redhatfirefox-0:140.9.0-1.el8_22026-04-13redhat
redhatfirefox-0:140.9.0-1.el9_42026-04-13redhat
redhatfirefox-0:140.9.0-1.el10_02026-04-13redhat
redhatfirefox-0:140.9.0-1.el9_02026-04-13redhat
redhatfirefox-0:140.9.0-1.el8_62026-04-13redhat
redhatfirefox-0:140.9.0-1.el8_82026-04-13redhat
redhatfirefox-0:140.9.0-1.el9_22026-04-13redhat
redhatfirefox-0:140.9.0-1.el9_62026-04-13redhat
redhatfirefox-0:140.9.0-1.el8_42026-04-13redhat
redhatthunderbird-0:140.9.0-1.el8_102026-04-07redhat
redhatthunderbird-0:140.9.0-1.el10_12026-04-01redhat
redhatthunderbird-0:140.9.0-1.el9_72026-03-30redhat
redhatfirefox-0:140.9.0-1.el9_72026-03-26redhat
redhatfirefox-0:140.9.0-1.el8_102026-03-26redhat
redhatfirefox-0:140.9.0-1.el10_12026-03-26redhat

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 (255 versions)140.9.0esr-1~deb11u1—
thunderbird1:102.0.1-1 ... 1:91.9.0-1~deb9u1 (306 versions)1:140.9.0esr-1~deb11u1—
Debian:12(2)
PackageVulnerable rangeFixed inDependents
firefox-esr102.11.0esr-1 ... 140.8.0esr-1~deb13u1 (161 versions)140.9.0esr-1~deb12u1—
thunderbird1:102.11.0-1 ... 1:140.9.0esr-1~deb11u1 (191 versions)1:140.9.0esr-1~deb12u1—
Debian:13(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.8.0esr-1~deb13u1 (36 versions)140.9.0esr-1~deb13u1—
thunderbird1:128.13.0esr-1 ... 1:140.9.0esr-1~deb11u1 (46 versions)1:140.9.0esr-1~deb13u1—
Debian:14(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.0esr-1~deb13u1 (39 versions)140.9.0esr-1—
thunderbird1:128.13.0esr-1 ... 1:140.9.0esr-1~deb13u1 (48 versions)1:140.9.0esr-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(5)

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 / 88× 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 241 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-4720?
CVE-2026-4720 is a critical vulnerability published on March 24, 2026. Memory safety bugs present in Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. 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…
When was CVE-2026-4720 disclosed?
CVE-2026-4720 was first published in the National Vulnerability Database on March 24, 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-2026-4720 actively exploited?
CVE-2026-4720 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 64.5% of all scored CVEs.
What is the CVSS score of CVE-2026-4720?
CVE-2026-4720 has a CVSS v3.1 base score of 9.8 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-4720?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-4720, 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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