When interacting with an HTML input element's file picker dialog with webkitdirectory set, a use-after-free could have resulted, leading to memory corruption and a potentially exploitable crash. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-38504
• https://bugzilla.mozilla.org/show_bug.cgi?id=1730156
• https://www.mozilla.org/security/advisories/mfsa2021-48/
• https://www.mozilla.org/security/advisories/mfsa2021-49/
• https://www.mozilla.org/security/advisories/mfsa2021-50/
• https://www.debian.org/security/2021/dsa-5026
• https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html
• https://www.debian.org/security/2022/dsa-5034
• https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html
• https://security.gentoo.org/glsa/202202-03
• https://security.gentoo.org/glsa/202208-14