CVE-2023-4577

Name: CVE-2023-4577
Creator: NVD / NIST
Published: 2023-09-11T09:15:09.287+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 0.55%

Last modified Jun 17, 2026

CVE-2023-4577 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. When `UpdateRegExpStatics` attempted to access `initialStringHeap` it could already have been garbage collected prior to entering the function, which could potentially have led to an exploitable crash. This vulnerability affects Firefox < 117, Firefox ESR < 115.2, and Thunderbird < 115.2.. EPSS estimates a 0.55% chance of exploitation in the next 30 days.

Description

When `UpdateRegExpStatics` attempted to access `initialStringHeap` it could already have been garbage collected prior to entering the function, which could potentially have led to an exploitable crash. This vulnerability affects Firefox < 117, Firefox ESR < 115.2, and Thunderbird < 115.2.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

0.55%

42.0th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 117.0
Mozilla	Firefox Esr	< 115.2
Mozilla	Thunderbird	< 115.2

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1847397Issue Tracking, Permissions Required
https://www.mozilla.org/security/advisories/mfsa2023-34/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2023-36/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2023-38/Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1847397Issue Tracking, Permissions Required
https://www.mozilla.org/security/advisories/mfsa2023-34/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2023-36/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2023-38/Vendor Advisory

Timeline

Published: Sep 11, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-4577?

How severe is CVE-2023-4577?

CVE-2023-4577 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.55% probability of exploitation in the next 30 days.

How do I fix CVE-2023-4577?

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-2023-4577?

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

Scan your code now

Source: NVD / NIST