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Fencer Vulns
low 2.5

CVE-2021-29948 json

Signatures are written to disk before and read during verification, which might be subject to a race condition when a malicious local proce…

published 2021-06-24 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-16407

cvss
2.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 21%
public exploits
0
none known

Summary

Signatures are written to disk before and read during verification, which might be subject to a race condition when a malicious local process or user is replacing the file. This vulnerability affects Thunderbird < 78.10.

Patch / fix

  • Mozilla Thunderbird 78.10
  • thunderbird Debian 14, Debian 13, Debian 12 1:78.10.0-1

debian advisories DEBIAN-CVE-2021-29948

  • thunderbird Ubuntu 18.04 LTS 1:78.11.0+build1-0ubuntu0.18.04.2
  • thunderbird Ubuntu 20.04 LTS 1:78.11.0+build1-0ubuntu0.20.04.2

ubuntu advisories UBUNTU-CVE-2021-29948

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

  • thunderbird RHEL 8 78.10.0-1.el8_3
  • thunderbird RHEL 7 78.10.0-1.el7_9
  • thunderbird RHEL 8.1 EUS 78.10.0-1.el8_1
  • thunderbird RHEL 8.2 EUS 78.10.0-1.el8_2

red hat advisories RHSA-2021:1351RHSA-2021:1353RHSA-2021:1350RHSA-2021:1352

  • MozillaThunderbird SLE Workstation Extension 15 SP2 78.10.0-8.23.1

suse advisories SUSE-SU-2021:1432-1

  • MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1
  • MozillaThunderbird openSUSE Leap 15.2 78.10.0-lp152.2.41.1

opensuse advisories openSUSE-SU-2024:10601-1openSUSE-SU-2021:0644-1

  • thunderbird Alpine 3.23, Alpine 3.22, Alpine 3.21 +5 more 91.3.2-r0

alpine advisories ALPINE-CVE-2021-29948

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

  • thunderbird Arch Linux 78.10.0-1

arch linux advisories AVG-1836

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-29948 updated cvss 2.5

Mozilla: Race condition when reading from disk while verifying signatures

  • Red Hat Enterprise Linux 6 thunderbird
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) thunderbird 78.10.0-1.el8_3
    fixed: vendor fix RHSA-2021:1353
  • Red Hat Enterprise Linux AppStream EUS (v. 8.1) thunderbird 78.10.0-1.el8_1
    fixed: vendor fix RHSA-2021:1351
  • Red Hat Enterprise Linux AppStream EUS (v. 8.2) thunderbird 78.10.0-1.el8_2
    fixed: vendor fix RHSA-2021:1352
  • Red Hat Enterprise Linux Client (v. 7) thunderbird 78.10.0-1.el7_9 Red Hat Enterprise Linux Server Optional (v. 7) thunderbird 78.10.0-1.el7_9 Red Hat Enterprise Linux Workstation (v. 7) thunderbird 78.10.0-1.el7_9
    fixed: vendor fix RHSA-2021:1350

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.29% chance of exploitation in the next 30 days, higher than 21% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugzilla.mozilla.org https://bugzilla.mozilla.org/show_bug.cgi?id=1692899 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 2.5 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
NVD 2.0 1.9 AV:L/AC:M/Au:N/C:N/I:P/A:N

Affected products

  • Mozilla Thunderbird

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization

References

Sources

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.