Due to incorrect JIT optimization, we incorrectly interpreted data from the wrong type of object, resulting in the potential leak of a sing…

published 2021-08-17 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-16441

cvss: 6.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.1%; EPSS 1.1% chance of exploitation in 30 days, percentile 66%
public exploits: 0; none known

Due to incorrect JIT optimization, we incorrectly interpreted data from the wrong type of object, resulting in the potential leak of a single bit of memory. This vulnerability affects Firefox < 91 and Thunderbird < 91.

Patch / fix

fixed in 2 distros 5

Mozilla Firefox 91
Mozilla Thunderbird 91

ubuntu suse opensuse alpine arch linux

firefox Ubuntu 18.04 LTS 91.0+build2-0ubuntu0.18.04.1
firefox Ubuntu 20.04 LTS 91.0+build2-0ubuntu0.20.04.1
thunderbird Ubuntu 18.04 LTS 1:91.5.0+build1-0ubuntu0.18.04.1
thunderbird Ubuntu 20.04 LTS 1:91.5.0+build1-0ubuntu0.20.04.1

ubuntu advisories UBUNTU-CVE-2021-29982

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +11 more 91.9.0-112.104.1
MozillaFirefox SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +7 more 91.9.0-150000.150.34.1
MozillaThunderbird SLE Workstation Extension 15 SP3, SLE Workstation Extension 15 SP2 91.4.0-8.45.2
MozillaFirefox SLE Module for Desktop Applications 15 SP3, SLE Module for Desktop Applications 15 SP2 91.2.0-8.54.1
MozillaFirefox-branding-SLE SLE Module for Desktop Applications 15 SP3, SLE Module for Desktop Applications 15 SP2 91-9.5.1
MozillaFirefox SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +7 more 91.2.0-3.155.2
MozillaFirefox-branding-SLE SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +7 more 91-4.19.1
MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +11 more 91.1.0-112.71.1

suse advisories SUSE-SU-2022:1582-1 SUSE-SU-2022:1577-1 SUSE-SU-2021:4150-1 SUSE-SU-2021:14826-1 SUSE-SU-2021:3451-1 SUSE-SU-2021:3331-1

firefox-esr openSUSE Tumbleweed 128.5.1-1.1
MozillaFirefox openSUSE Tumbleweed 92.0-1.2
MozillaThunderbird openSUSE Leap 15.2 91.4.0-lp152.2.52.1
MozillaThunderbird openSUSE Leap 15.3 91.4.0-8.45.2
MozillaFirefox openSUSE Leap 15.2 91.2.0-lp152.2.67.1
rust-cbindgen openSUSE Leap 15.2 0.19.0-lp152.2.7.1
MozillaFirefox openSUSE Leap 15.3 91.2.0-8.54.1
MozillaFirefox-branding-SLE openSUSE Leap 15.3 91-9.5.1

opensuse advisories openSUSE-SU-2024:14572-1 openSUSE-SU-2024:10600-1 openSUSE-SU-2021:1635-1 openSUSE-SU-2021:4150-1 openSUSE-SU-2021:1367-1 openSUSE-SU-2021:3451-1

firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +6 more 92.0.1-r0
librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 92.0.1-r0
thunderbird Alpine 3.23, Alpine 3.22, Alpine 3.21 +5 more 91.3.2-r0

alpine advisories ALPINE-CVE-2021-29982

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

firefox Arch Linux 91.0-1
thunderbird Arch Linux 91.1.0-1

arch linux advisories AVG-2269 AVG-2291

Exploit prediction

1.12% chance of exploitation in the next 30 days, higher than 66% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

bugzilla.mozilla.org https://bugzilla.mozilla.org/show_bug.cgi?id=1715318 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
NVD	2.0	4.3	AV:N/AC:M/Au:N/C:P/I:N/A:N

Affected products

Mozilla Firefox
Mozilla Thunderbird

Classification

Weakness

CWE-772 Missing Release of Resource after Effective Lifetime

References

bugzilla.mozilla.org /show_bug.cgi?id=1715318
exploit, issue-tracking, vendor-advisory
security.gentoo.org /glsa/202202-03
vendor-advisory, third-party-advisory
mozilla.org /security/advisories/mfsa2021-33/
vendor-advisory
mozilla.org /security/advisories/mfsa2021-36/
vendor-advisory

Sources

CVE List CVE-2021-29982
NVD CVE-2021-29982

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary