CVE-2021-43535

moderate-risk
Published 2021-12-08

A use-after-free could have occured when an HTTP2 session object was released on a different thread, leading to memory corruption and a potentially exploitable crash. This vulnerability affects Firefox < 93, Thunderbird < 91.3, and Firefox ESR < 91.3.

Do I need to act?

~
1.2% chance of exploitation in next 30 days
EPSS score — moderate exploit probability
-
Not on CISA KEV list
No confirmed active exploitation reported to CISA
?
Patch status unknown
Check vendor advisories for fix availability and mitigation guidance
8
CVSS 8.8/10 High
NETWORK / LOW complexity

Affected Products (6)

Affected Vendors

Debian Mozilla

References (16)

Issue Tracking https://bugzilla.mozilla.org/show_bug.cgi?id=1667102
Mailing List https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html
Mailing List https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html
Third Party Advisory https://www.debian.org/security/2021/dsa-5026
Issue Tracking https://www.debian.org/security/2022/dsa-5034
Vendor Advisory https://www.mozilla.org/security/advisories/mfsa2021-43/
Vendor Advisory https://www.mozilla.org/security/advisories/mfsa2021-49/
Vendor Advisory https://www.mozilla.org/security/advisories/mfsa2021-50/
Issue Tracking https://bugzilla.mozilla.org/show_bug.cgi?id=1667102
Mailing List https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html
Mailing List https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html
Third Party Advisory https://www.debian.org/security/2021/dsa-5026
Issue Tracking https://www.debian.org/security/2022/dsa-5034
Vendor Advisory https://www.mozilla.org/security/advisories/mfsa2021-43/
Vendor Advisory https://www.mozilla.org/security/advisories/mfsa2021-49/
Vendor Advisory https://www.mozilla.org/security/advisories/mfsa2021-50/
47
/ 100
moderate-risk
Severity 30/34 · Critical
Exploitability 4/34 · Minimal
Exposure 13/34 · Low