CVE-2021-29981
An issue present in lowering/register allocation could have led to obscure but deterministic register confusion failures in JITted code that would lead to a potentially exploitable crash.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (1.01%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
An issue present in lowering/register allocation could have led to obscure but deterministic register confusion failures in JITted code that would lead to a potentially exploitable crash. This vulnerability affects Firefox < 91 and Thunderbird < 91.
- CVSS 3.1
- 8.8 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- EPSS
- 1.01% probability · 63th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Affected
- mozilla/firefox · mozilla/thunderbird
- Source
- security@mozilla.org
EPSS 1.0% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1707774Issue Tracking, Vendor Advisory
- https://security.gentoo.org/glsa/202202-03Third Party Advisory
- https://www.mozilla.org/security/advisories/mfsa2021-33/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2021-36/Vendor Advisory
- https://bugzilla.mozilla.org/show_bug.cgi?id=1707774Issue Tracking, Vendor Advisory
- https://security.gentoo.org/glsa/202202-03Third Party Advisory
- https://www.mozilla.org/security/advisories/mfsa2021-33/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2021-36/Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.