CVE-2023-4577: Mozilla Firefox · Vulnerability
Affects Mozilla FirefoxSource CVE Database V5
Not known to be exploited : upgrade to 117 or 115.2 soon.
Data as of 25 Oct 2026, 21:28 UTC
Rated High by the CNA (mozilla) · No CVSS score from NVD or the CNA
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 117, 115.2
Exploitation evidence
Disclosed: evidence found.
CVE published 11 Sep 2023
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.
What to do
Upgrade Mozilla Firefox to 117 or 115.2.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Mozilla Firefox | Affected
| Fixed in
|
AI-suggested
Mozilla has released official fixes for this vulnerability in Firefox 117 and Firefox ESR/Thunderbird 115.2. Users and administrators should update to these versions or later to remediate the issue. Since this is a client-side application vulnerability, applying the official update is the primary mitigation. No additional vendor-recommended mitigations or workarounds are indicated.
Description
CVE-2023-4577 is a high-impact memory corruption vulnerability in Mozilla Firefox and Thunderbird's JIT engine. The flaw occurs when the function UpdateRegExpStatics attempts to access initialStringHeap, which may have already been garbage collected, potentially leading to an exploitable crash. This vulnerability affects Firefox versions prior to 117 and Firefox ESR and Thunderbird versions prior to 115.2. Mozilla has fixed this issue in Firefox 117 and Firefox ESR/Thunderbird 115.2. No known exploits in the wild have been reported as of the advisory date.