CVE-2025-4918: mozilla firefox Out-of-bounds Read
Vulnerability summary
CVE-2025-4918 is a critical (CVSS 9.8) Out-of-bounds Read vulnerability in mozilla firefox. EPSS estimates a 9.43% chance of exploitation in the next 30 days, higher than 95.3% of scored vulnerabilities. 2 public exploits are recorded.
Advisory lineage
Upstream 0 · Downstream 34 · Duplicates 1 · Related 8Timeline
- 17-05-2025PublishedVulnerability first disclosed.
- 13-04-2026Last modifiedVulnerability information updated.
Description
An attacker was able to perform an out-of-bounds read or write on a JavaScript `Promise` object. This vulnerability was fixed in Firefox 138.0.4, Firefox ESR 128.10.1, Firefox ESR 115.23.1, Thunderbird 128.10.2, and Thunderbird 138.0.2.
CVSS metrics
6 scores · 6 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · WolfiEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · ChainguardEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- NVDNIST9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
9.43%
Chance of exploitation in the next 30 days
Percentile
95%
Versus all other CVEs
30-day change
+0.05 pp
From 9.38% on 20-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
2 foundExploit Reference (vicarius.io)
Maturity: unknown
Exploit Reference (vicarius.io)
Maturity: unknown
Weaknesses
CWE · root causeAffected systems
Ubuntu8 products
- mozjs102All versions (No fix recorded)
- mozjs115All versions (No fix recorded)
- mozjs38All versions (No fix recorded)
- mozjs52All versions (No fix recorded)
- mozjs68All versions (No fix recorded)
Chainguard2 products
- firefox< 128.10.1-r0
- firefox-esr< 115.23.1-r0
Debian2 products
- firefox-esr< 128.10.1esr-1~deb12u1 | < 128.10.1esr-1
- thunderbird< 1:128.11.0esr-1~deb12u1 | < 1:128.11.0esr-1
Mozilla2 products
- firefox< 115.23.1 | < 138.0.4 | ≥ 116.0, < 128.10.1
- thunderbird< 128.10.2 | ≥ 138.0, < 138.0.2
Wolfi1 product
- firefox< 128.10.1-r0
5 vendors · 15 products
References
15 links- www.vicarius.io/vsociety/posts/cve-2025-4918-detect-firefox-out-of-bounds-writeEVIDENCEExploitThird Party Advisory
- www.vicarius.io/vsociety/posts/cve-2025-4918-mitigate-firefox-out-of-bounds-writeEVIDENCEExploitThird Party Advisory
