CVE-2026-12299: mozilla firefox Type Confusion
CVSS: 5.4v3.1MediumModified
AliasesUBUNTU-CVE-2026-12299DEBIAN-CVE-2026-12299CGA-9c72-9jvq-j24hCGA-c4cp-4q6f-f5vgCGA-8qfc-fmpc-qrvxCGA-px8q-6fw9-443f
Published 16-06-2026Last modified 15-07-2026
Vulnerability summary
CVE-2026-12299 is a medium (CVSS 5.4) Type Confusion vulnerability in mozilla firefox. EPSS estimates a 0.31% chance of exploitation in the next 30 days, higher than 21.9% of scored vulnerabilities.
CVSS score
5.4/10
010
Medium · v3.1 (CVE.org)EPSS score
0.31%
0%100%
Low · 0.00 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 37 · Related 14MGASA-2026-0242MGASA-2026-0243MGASA-2026-0326OPENSUSE-SU-2026:11052-1OPENSUSE-SU-2026:11055-1OPENSUSE-SU-2026:11072-1OPENSUSE-SU-2026:21043-1OPENSUSE-SU-2026:21168-1OPENSUSE-SU-2026:21519-1RHSA-2026:27717RHSA-2026:27733RHSA-2026:27734RHSA-2026:29940RHSA-2026:30846RHSA-2026:33445RHSA-2026:36100RHSA-2026:36101RHSA-2026:36102RHSA-2026:36103RHSA-2026:37210RHSA-2026:37391RHSA-2026:38506RHSA-2026:38750RHSA-2026:38751RHSA-2026:38753RHSA-2026:39011RHSA-2026:39141RHSA-2026:39142RHSA-2026:39428RHSA-2026:39706SUSE-SU-2026:22351-1SUSE-SU-2026:23115-1SUSE-SU-2026:23137-1SUSE-SU-2026:2582-1SUSE-SU-2026:2583-1SUSE-SU-2026:2814-1SUSE-SU-2026:2852-1CGA-XMC9-RCMC-M2RR
Timeline
- 16-06-2026PublishedVulnerability first disclosed.
- 15-07-2026Last modifiedVulnerability information updated.
Description
JIT miscompilation in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
CVSS metrics
4 scores · 4 sources · 1 versionMedium 5.4Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:NSources4 sources · 5.4–7.5
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:HDiffers
- OSV · DebianEcosystem advisory · calculated5.4MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
- NVDNIST5.4MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
EPSS trend
Probability
0.31%
Chance of exploitation in the next 30 days
Percentile
22%
Versus all other CVEs
30-day change
0.00 pp
From 0.31% on 19-09-2026
19-09-202619-10-2026
EPSS score0.31%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-843Access of Resource Using Incompatible Type ('Type Confusion')The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.
- CWE-733Compiler Optimization Removal or Modification of Security-critical CodeThe developer builds a security-critical protection mechanism into the software, but the compiler optimizes the program such that the mechanism is removed or modified.
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< 140.12.0-r0
- firefox-esr< 140.12.0-r0
Debian2 products
- firefox-esr< 140.12.0esr-1~deb12u1 | < 140.12.0esr-1~deb13u1 | < 140.12.0esr-1
- thunderbird< 1:140.12.0esr-1~deb12u1 | < 1:140.12.0esr-1~deb13u1 | < 1:140.12.0esr-1
Mozilla2 products
- firefox< 115.37.0 | < 152.0 | ≥ 140.0, < 140.12.0
- thunderbird< 152.0.0 | ≥ 140.0, < 140.12.0
Wolfi1 product
- firefox< 140.12.0-r0
5 vendors · 15 products
References
36 links- bugzilla.mozilla.org/show_bug.cgi?id=2043139Permissions Required
- www.mozilla.org/security/advisories/mfsa2026-57/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-58/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-59/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-60/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-61/Vendor Advisory
