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CVE-2025-11721

CRITICALCVSS 9.8/10EPSS 0.33%

Last modified

CVE-2025-11721 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Memory safety bug present in Firefox 143 and Thunderbird 143. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. EPSS estimates a 0.33% chance of exploitation in the next 30 days.

Description

Memory safety bug present in Firefox 143 and Thunderbird 143. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 144 and Thunderbird 144.

Metrics

CVSS 3.1
9.8/10

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

EPSS Probability
0.33%

25.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
MozillaFirefox>= 143.0, < 144.0
MozillaThunderbird>= 143.0, < 144.0

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2025-11721?
Memory safety bug present in Firefox 143 and Thunderbird 143. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 144 and Thunderbird 144.
How severe is CVE-2025-11721?
CVE-2025-11721 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.33% probability of exploitation in the next 30 days.
How do I fix CVE-2025-11721?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-11721?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST