CVE-2026-6754: Use-after-free in the JavaScript Engine component
Modified
AliasesUBUNTU-CVE-2026-6754DEBIAN-CVE-2026-6754CGA-8684-5h96-g9gcCGA-8mrc-rccw-xphfCGA-773f-8vhj-fjpfCGA-m6v9-pvv5-jfq6
Published 21-04-2026Last modified 15-07-2026
Vulnerability summary
CVE-2026-6754 is a high (CVSS 7.5) Use After Free vulnerability in mozilla firefox. EPSS estimates a 0.58% chance of exploitation in the next 30 days, higher than 46.8% of scored vulnerabilities.
CVSS score
7.5/10
010
High · v3.1 (CVE.org)EPSS score
0.58%
0%100%
Low · +0.19 pp in 30 daysKEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 32 · Related 4MGASA-2026-0124MGASA-2026-0125OPENSUSE-SU-2026:10610-1OPENSUSE-SU-2026:10626-1OPENSUSE-SU-2026:11373-1RHSA-2026:10757RHSA-2026:10766RHSA-2026:10767RHSA-2026:12285RHSA-2026:13537RHSA-2026:15892RHSA-2026:17477RHSA-2026:17687RHSA-2026:17688RHSA-2026:17689RHSA-2026:17690RHSA-2026:19041RHSA-2026:19131RHSA-2026:19201RHSA-2026:19348RHSA-2026:19461RHSA-2026:19462RHSA-2026:19463RHSA-2026:19464RHSA-2026:19465RHSA-2026:19466RHSA-2026:19467RHSA-2026:19468RHSA-2026:19469RHSA-2026:19542RHSA-2026:19655RHSA-2026:19704CGA-65JH-3QQ9-M2PX
Timeline
- 21-04-2026PublishedVulnerability first disclosed.
- 15-07-2026Last modifiedVulnerability information updated.
Description
Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
CVSS metrics
4 scores · 4 sources · 1 versionHigh 7.5Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HSourcesAll 4 agree
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.58%
Chance of exploitation in the next 30 days
Percentile
47%
Versus all other CVEs
30-day change
Increase +0.19 pp
From 0.39% on 22-09-2026
22-09-202622-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
- CWE-825Expired Pointer DereferenceThe product dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.
Affected 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< 140.10-r0
- firefox-esr< 140.10-r0
Debian2 products
- firefox-esr< 140.10.0esr-1~deb12u1 | < 140.10.0esr-1~deb13u1 | < 140.10.0esr-1
- thunderbird< 1:140.10.0esr-1~deb12u1 | < 1:140.10.0esr-1~deb13u1 | < 1:140.10.0esr-1
Mozilla2 products
- firefox< 115.35.0 | < 150.0 | ≥ 140.0, < 140.10.0
- thunderbird< 140.10.0
Wolfi1 product
- firefox< 140.10-r0
5 vendors · 15 products
References
41 links- bugzilla.mozilla.org/show_bug.cgi?id=2027541Permissions Required
- www.mozilla.org/security/advisories/mfsa2026-30/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-31/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-32/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-33/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-34/Vendor Advisory
