How severe is CVE-2023-4577?

CVE-2023-4577 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2023-4577 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-4577?

CVE-2023-4577 primarily affects Mozilla Firefox. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2023-4577?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2023-4577 published?

CVE-2023-4577 was published on 2023-09-11 and last updated on 2026-06-17.

CVE-2023-4577

CVE-2023-4577 is a medium-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 1% (42nd percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Mozilla Firefox
Published: 2023-09-11
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2023-4577?: 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.
How severe is CVE-2023-4577?: CVE-2023-4577 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2023-4577 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-4577?: CVE-2023-4577 primarily affects Mozilla Firefox. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2023-4577?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2023-4577 published?: CVE-2023-4577 was published on 2023-09-11 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

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