CVE-2026-12327
HIGH 8.1Memory safety bugs present in 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, Thunderbird 152, and Thunderbird 140.12.
Severe if exploited (CVSS 8.1), but no known exploitation and low modeled probability. Patch on a normal cadence.
Exploitation likelihood
0.4%chance of exploitation in 30 days · 33rd percentile
Impact if exploited
8.1CVSS 3.1 · HIGH
- ConfidentialityHigh
- IntegrityHigh
- AvailabilityHigh
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ✓Privileges: No account or privileges required
- ✓User interaction: No user interaction needed
- ⚠Complexity: Needs a race window or specific setup
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept & exploit code
- github-search Search GitHub for public PoC repos
Test against your own equipment
curl -s https://vulnpedia.com/cve/CVE-2026-12327/poc.jsonMachine-readable PoC index for this CVE (for automation).Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-12327/poc.json
Weakness (CWE)
- CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Known Affected Software Configurations
| Vendor | Product | Version range |
|---|---|---|
| Mozilla | Firefox | < 115.37.0 |
| Mozilla | Firefox | < 152.0.0 |
| Mozilla | Firefox | ≥ 140.0 and < 140.12.0 |
| Mozilla | Thunderbird | < 152.0.0 |
| Mozilla | Thunderbird | ≥ 140.0 and < 140.12.0 |
All CVSS metrics
- HIGH 8.1 v3.1 · ADP Primary
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H - HIGH 8.1 v3.1 · NVD Secondary
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H