CVE-2026-22701: filelock Time-of-Check-Time-of-Use (TOCTOU) Symlink Vulnerability in SoftFileLock
Noroxi assessment
Priority: Monitor (action score 21/100)
- 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: 0.12% (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: tox-dev filelock 3.20.3; azl3 python-filelock 3.20.1-1 on Azure Linux 3.0 3.20.3-1; cbl2 python-filelock 3.0.12-13 on CBL Mariner 2.0 3.0.12-14.
Low priority for now. Upgrade to tox-dev filelock 3.20.3; azl3 python-filelock 3.20.1-1 on Azure Linux 3.0 3.20.3-1; cbl2 python-filelock 3.0.12-13 on CBL Mariner 2.0 3.0.12-14 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
filelock is a platform-independent file lock for Python. Prior to version 3.20.3, a TOCTOU race condition vulnerability exists in the SoftFileLock implementation of the filelock package. An attacker with local filesystem access and permission to create symlinks can exploit a race condition between the permission validation and file creation to cause lock operations to fail or behave unexpectedly. The vulnerability occurs in the _acquire() method between raise_on_not_writable_file() (permission check) and os.open() (file creation). During this race window, an attacker can create a symlink at the lock file path, potentially causing the lock to operate on an unintended target file or leading to denial of service. This issue has been patched in version 3.20.3.
- Published
- Jan 10, 2026
- Updated
- Jun 17, 2026
- EPSS
- 0.1% · 2th percentile
- CWE
- CWE-59
Report tools
Action score
21
Monitor
Low priority for now.
- CVSS
- 21 / 40 · 5.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.1%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · GitHub_M
- 5.3
- NVD has not scored this yet; the score shown is the CNA’s.
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.
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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.
We use this product, ask for helpAffected 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.
| Vendor | Product | CPE |
|---|---|---|
| tox-dev | filelock | cpe:2.3:a:tox-dev:filelock |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- tox-dev filelockbefore 3.20.3
Versions reported by the vendor
Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.
tox-dev filelock
- < 3.20.3affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | python-filelock | before 3.9.0-1+deb12u1 | 3.9.0-1+deb12u1 |
| Debian:13 | python-filelock | from 0 | — |
| Debian:14 | python-filelock | before 3.20.3-1 | 3.20.3-1 |
| openSUSE:Leap 15.6 | python-filelock | before 3.12.2-150400.10.8.1 | 3.12.2-150400.10.8.1 |
| openSUSE:Leap 16.0 | python-filelock | before 3.18.0-160000.3.1 | 3.18.0-160000.3.1 |
| openSUSE:Tumbleweed | python-filelock | before 3.20.3-1.1 | 3.20.3-1.1 |
| PyPI | filelock | before 3.20.3 | 3.20.3 |
| SUSE:Linux Enterprise Module for Development Tools 15 SP7 | python-filelock | before 3.0.12-150100.3.9.1 | 3.0.12-150100.3.9.1 |
| SUSE:Linux Enterprise Module for Python 3 15 SP7 | python-filelock | before 3.12.2-150400.10.8.1 | 3.12.2-150400.10.8.1 |
| SUSE:Linux Enterprise Server 16.0 | python-filelock | before 3.18.0-160000.3.1 | 3.18.0-160000.3.1 |
Same product
tox-dev: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-112940filelock ReadWriteLock: SQLite reopens the lock database by name, so a planted symlink or journal file makes the lock user's process overwrite or unlink its own28Monitor
- CVE-2025-68146filelock has TOCTOU race condition that allows symlink attacks during lock file creation26Monitor
- CVE-2026-112911filelock: StrictSoftFileLock and SoftReadWriteLock adopt a protocol directory another user created first, losing mutual exclusion25Monitor
Published before and after this one in the same product
- Later →CVE-2026-112906Oct 20, 2026 · filelock: SoftFileLock evicts a fresh lock file whose watched age another local user's pre-dated file passed on through inode reuse18Monitor
- Later →CVE-2026-112909Oct 20, 2026 · filelock: UnixFileLock truncates and chmods any regular file another user renames or hard-links onto the lock path24Monitor
- Later →CVE-2026-112912Oct 20, 2026 · filelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists and is writable by the lock taker10Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| tox-dev filelock | 3.20.3 · description | Vendor (CNA) |
| azl3 python-filelock 3.20.1-1 on Azure Linux 3.0 | 3.20.3-1 · CBL-Mariner Releases | Microsoft (MSRC) |
| cbl2 python-filelock 3.0.12-13 on CBL Mariner 2.0 | 3.0.12-14 · CBL-Mariner Releases | Microsoft (MSRC) |
| cbl2 python-filelock 3.0.12-13 on CBL-Mariner 2.0 | 3.0.12-14 · Release Notes | Microsoft (MSRC) |
| debian:python-filelock | 3.9.0-1+deb12u1 · Debian:12 | Package registry (OSV) |
| opensuse:python-filelock | 3.12.2-150400.10.8.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| PyPI:filelock | 3.20.3 | Package registry (OSV) |
| suse:python-filelock | 3.12.2-150400.10.8.1 · SUSE:Linux Enterprise Module for Python 3 15 SP7 | Package 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.
No history yet (it accumulates with the daily EPSS job).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2025-6814625 days apartfilelock has TOCTOU race condition that allows symlink attacks during lock file creation26Monitor
- CVE-2026-112936283 days apartfilelock: ReadWriteLock follows a symlink at the lock path into SQLite24Monitor
- CVE-2026-112912283 days apartfilelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists and is writable by the lock taker10Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
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
- none
- Integrity
- low · 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
- None
- Integrity impact
- Low
- Availability impact
- High
Weakness class (CWE)
CWE-59 · Improper Link Resolution Before File Access ('Link Following')CVSS vector
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
ATT&CK techniques
- Obfuscated Files or Information: HTML SmugglingT1027.006
- Obfuscated Files or Information: Embedded PayloadsT1027.009
- Boot or Logon Autostart Execution:Shortcut ModificationT1547.009
- Hide Artifacts: Resource ForkingT1564.009
- Hijack Execution Flow: Executable Installer File Permissions WeaknessT1574.005
- Hijack Execution Flow: Services File Permissions WeaknessT1574.010
Change log
- Fix✗ → ✓
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References
Show all references (2 more)Show less
Vendor advisories and official records. Exploit/PoC links are deliberately left out.