CVE-2026-12328: mozilla firefox Classic Buffer Overflow
Vulnerability summary
CVE-2026-12328 is a high (CVSS 8.1) Classic Buffer Overflow vulnerability in mozilla firefox. EPSS estimates a 0.48% chance of exploitation in the next 30 days, higher than 39.7% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 37 · Related 14Timeline
- 16-06-2026PublishedVulnerability first disclosed.
- 15-07-2026Last modifiedVulnerability information updated.
Description
Memory safety bugs present in Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird ESR 140.11, Firefox 151 and Thunderbird 151. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. 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 version- 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 · calculated8.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- NVDNIST8.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.48%
Chance of exploitation in the next 30 days
Percentile
40%
Versus all other CVEs
30-day change
0.00 pp
From 0.48% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
- 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DereferenceThe product dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.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< 140.12.0-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/buglist.cgiBroken Link
- 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
