VulnTideExploited vulnerabilities, by vendor. Data as of .
Not in CISA KEVPublished CVSS 9.8 criticalEPSS 0.7% probability of exploitation in 30 days
Mozilla

CVE-2026-74987: Internally found bugs fixed in Firefox ESR 140.14, Firefox ESR 153.1 and Firefox 154

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?
0.7%

EPSS score, percentile 53.7 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?
9.8 Critical

CVSS v3.1 base score, from CISA's enrichment of the record

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

The CVE record links no vendor advisory, patch or mitigation.

Which versions are affected?

Unaffected 140.14; 153.1; 154; 140.14; 153.1; 154

Versions by product

Source: CISA KEV 2026.10.29, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.

What to do

Advisories and patches

The CVE record links no vendor advisory, patch or mitigation.

This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Mozilla Firefox
StatusVersions
Unaffected140.14
Unaffected153.1
Unaffected154
Mozilla Thunderbird
StatusVersions
Unaffected140.14
Unaffected153.1
Unaffected154

Versions the record lists as unaffected: 140.14, 153.1, 154.

Source: CVE List, as of . About the data.

About this vulnerability

Internally found bugs present in Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 15…

Summary: CVE record, as of .

  • CISA has not added CVE-2026-74987 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
  • The CVE record was published on 18 Aug 2026.
  • The CVE record carries a CVSS v3.1 base score of 9.8 (Critical), taken from CISA's enrichment of the record.
  • FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.7% (percentile 53.7), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
  • CISA's SSVC assessment in the CVE record: exploitation none, automatable yes, technical impact total.

Source: CISA KEV 2026.10.29, as of ; CVE List, as of ; FIRST EPSS, as of . About the data.

Description

Internally found bugs fixed in Firefox ESR 140.14, Firefox ESR 153.1 and Firefox 154

Internally found bugs present in Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

Source: CVE List, as of . About the data.

Weakness

CWE-119
  • CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.

Timeline

DateEvent
CVE record published
CVE record last updated

References

9

Known exploited Mozilla vulnerabilities

  • CVE-2010-3765: Mozilla Multiple Products Remote Code Execution Vulnerability (added )
  • CVE-2024-9680: Mozilla Firefox Use-After-Free Vulnerability (added )
  • CVE-2016-9079: Mozilla Firefox, Firefox ESR, and Thunderbird Use-After-Free Vulnerability (added )
  • CVE-2015-4495: Mozilla Firefox Security Feature Bypass Vulnerability (added )
  • CVE-2019-11707: Mozilla Firefox and Thunderbird Type Confusion Vulnerability (added )