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Fencer Vulns
high 7.8

CVE-2021-26910 json

Firejail before 0.9.64.4 allows attackers to bypass intended access restrictions because there is a TOCTOU race condition between a stat op…

published 2021-02-08 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-13694

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 39%
public exploits
0
none known

Summary

Firejail before 0.9.64.4 allows attackers to bypass intended access restrictions because there is a TOCTOU race condition between a stat operation and an OverlayFS mount operation.

Patch / fix

  • firejail_project firejail 0.9.64.4
  • firejail Debian 14, Debian 13, Debian 12 0.9.64.4-1

debian advisories DEBIAN-CVE-2021-26910

  • firejail Ubuntu 20.04 LTS 0.9.62-3ubuntu0.1

ubuntu advisories UBUNTU-CVE-2021-26910

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

  • firejail openSUSE Leap 15.2 0.9.64.4-lp152.3.6.1

opensuse advisories openSUSE-SU-2021:0271-1

  • firejail Alpine 3.13 0.9.64.4-r0

alpine advisories ALPINE-CVE-2021-26910

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

  • firejail Arch Linux 0.9.64.4-1

arch linux advisories AVG-1545

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-2021-26910 updated cvss 7.8

firejail: root privilege escalation

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

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

0.45% chance of exploitation in the next 30 days, higher than 39% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • openwall.com http://www.openwall.com/lists/oss-security/2021/02/09/1 referenced PoC, tagged "exploit" by a source, unverified
  • unparalleled.eu https://unparalleled.eu/publications/2021/advisory-unpar-2021-0.txt referenced PoC, tagged "exploit" by a source, unverified
  • unparalleled.eu https://unparalleled.eu/blog/2021/20210208-rigged-race-against-firejail-for-local-root/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AC:L/AV:L/A:H/C:H/I:H/PR:L/S:U/UI:N
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 7.0 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.9 AV:L/AC:M/Au:N/C:C/I:C/A:C

Classification

Weakness
  • CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

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.