Is CVE-2025-6436 in the CISA KEV catalog?

No. CVE-2025-6436 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2025-6436?

CVE-2025-6436 has a CVSS v3 base score of 8.1 (HIGH).

What is the EPSS score for CVE-2025-6436?

CVE-2025-6436 has an EPSS score of 2.88% (85th percentile), estimating the probability of exploitation in the next 30 days.

CVE & CISA-KEV Catalog

CVE-2025-6436

HIGHEPSS 85th pctl

8.1

CVSS v3

NVD

Description

Memory safety bugs present in Firefox 139 and Thunderbird 139. 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 140 and Thunderbird 140.

CWE-119Buffer Overflow

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploit Intelligence

2.88%probability of exploitation in 30 days

85thpercentile

Elevated risk: more likely to be exploited than 85% of all known CVEs.

References

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-13.