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NVD / CVE Program· CNA mitre

CVE-2021-26910: Firejail before 0.9.64.4 allows attackers to bypass intended access restrictions because there is a TOCTOU race condition between a stat…

HighCVSS 7.0 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 28/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.45% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: firejail (Alpine:v3.13) 0.9.64.4-r0; firejail (Debian:10) 0.9.58.2-2+deb10u2; firejail (Debian:12) 0.9.64.4-1.

Low priority for now. Upgrade to firejail (Alpine:v3.13) 0.9.64.4-r0; firejail (Debian:10) 0.9.58.2-2+deb10u2; firejail (Debian:12) 0.9.64.4-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published
Feb 8, 2021
Updated
Jun 16, 2026
EPSS
0.4% · 39th percentile

Report tools

JSON

Action score

28

Monitor

Low priority for now.

CVSS
28 / 40 · 7.0 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CNA vs NVD score

NVD
7.0
CNA · mitre
7.8
0.8 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-26910

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
firejail projectfirejail
debiandebian linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux10.0
  • debian debian linux9.0
  • firejail project firejailbefore 0.9.64.4

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Alpine:v3.13firejailbefore 0.9.64.4-r00.9.64.4-r0
Debian:10firejailbefore 0.9.58.2-2+deb10u20.9.58.2-2+deb10u2
Debian:12firejailbefore 0.9.64.4-10.9.64.4-1
Debian:9firejailbefore 0.9.44.8-2+deb9u20.9.44.8-2+deb9u2
openSUSE:Leap 15.2firejailbefore 0.9.64.4-lp152.3.6.10.9.64.4-lp152.3.6.1

Same product

firejail project: all records

Other highest-scoring records for the same primary product.

  • CVE-2020-17368Firejail through 0.9.62 mishandles shell metacharacters during use of the --output or --output-stderr option, which may lead to command…
    40Plan
  • CVE-2019-12589In Firejail before 0.9.60, seccomp filters are writable inside the jail, leading to a lack of intended seccomp restrictions for a process…
    35Monitor
  • CVE-2017-5940Firejail before 0.9.44.6 and 0.9.38.x LTS before 0.9.38.10 LTS does not comprehensively address dotfile cases during its attempt to prevent…
    35Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2019-12499May 31, 2019 · Firejail before 0.9.60 allows truncation (resizing to length 0) of the firejail binary on the host by running exploit code inside a…
    33Monitor
  • ← EarlierCVE-2020-17367Aug 11, 2020 · Firejail through 0.9.62 does not honor the -- end-of-options indicator after the --output option, which may lead to command injection.
    31Monitor
  • Later →CVE-2022-31214Jun 9, 2022 · A Privilege Context Switching issue was discovered in join.c in Firejail 0.9.68.
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
alpine:firejail0.9.64.4-r0 · Alpine:v3.13Package registry (OSV)
debian:firejail0.9.64.4-1 · Debian:12Package registry (OSV)
opensuse:firejail0.9.64.4-lp152.3.6.1 · openSUSE:Leap 15.2Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Not on record for this CVE: EPSS history · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

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

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records