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CVE-2021-26910

23
FAUCET Score

CVE-2021-26910 is a high-severity Time-of-Check to Time-of-Use (TOCTOU) race condition vulnerability affecting Firejail versions prior to 0.9.64.4, including various Debian Linux distributions. This flaw allows a local attacker to bypass intended access restrictions by manipulating the timing between a stat operation and an OverlayFS mount. With a CVSS score of 7.0, successful exploitation could lead to high confidentiality, integrity, and availability impacts, though it requires high attack complexity. Currently, there is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 0.9.64.4CPE matchmatch criteria
cpe:2.3:a:firejail_project:firejail:*:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.8HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
1.8
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.44%
Probability of exploitation in next 30 days
EPSS Percentile
36.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0044 is in the 77th percentile among its peer group of 1,525 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.4 InfoSec Media, 0.1 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

github.com / netblue30/firejail/commit/97d8a03cad19501f017587cc4e47d8418273834b
PatchThird Party Advisory
github.com / netblue30/firejail/releases/tag/0.9.64.4
Release NotesThird Party Advisory
lists.debian.org / debian-lts-announce/2021/02/msg00015.html
Third Party Advisory
security.gentoo.org / glsa/202105-19
Third Party Advisory
unparalleled.eu / blog/2021/20210208-rigged-race-against-firejail-for-local-root
ExploitThird Party Advisory
unparalleled.eu / publications/2021/advisory-unpar-2021-0.txt
ExploitThird Party Advisory
debian.org / security/2021/dsa-4849
Third Party Advisory
openwall.com / lists/oss-security/2021/02/09/1
ExploitMailing ListPatchThird Party Advisory