mlflow/mlflow: Creation of Temporary File With Insecure Permissions
CVE-2026-4137 is a high-severity creation of temporary file with insecure permissions vulnerability in mlflow/mlflow from Mlflow, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists version 3.11.0 as the first without the flaw, so updating mlflow/mlflow to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.19% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update mlflow/mlflow to 3.11.0 or a later version.
- Update Mlflow to 3.11.0 or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Mlflow | mlflow/mlflow | before 3.11.0 | 3.11.0 |
| Lfprojects | Mlflow | before 3.11.0 | 3.11.0 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 3.0 | 7.0 | High | CNA (huntr.dev) |
Official description
In mlflow/mlflow versions prior to 3.11.0, the `get_or_create_nfs_tmp_dir()` function in `mlflow/utils/file_utils.py` creates temporary directories with world-writable permissions (0o777), and the `_create_model_downloading_tmp_dir()` function in `mlflow/pyfunc/__init__.py` creates directories with group-writable permissions (0o770). These insecure permissions allow local attackers to tamper with model artifacts, such as cloudpickle-serialized Python objects, and achieve arbitrary code execution when the tampered artifacts are deserialized via `cloudpickle.load()`. This vulnerability is particularly critical in environments with shared NFS mounts, such as Databricks, where NFS is enabled by default. The issue is a continuation of the vulnerability class addressed in CVE-2025-10279, which was only partially fixed.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Creation of Temporary File With Insecure Permissions
Opening temporary files without appropriate measures or controls can leave the file, its contents and any function that it impacts vulnerable to attack.
How developers prevent this class of flaw
- Many contemporary languages have functions which properly handle this condition. Older C temp file functions are especially susceptible.
- Ensure that you use proper file permissions. This can be achieved by using a safe temp file function. Temporary files should be writable and readable only by the process that owns the file.
- Randomize temporary file names. This can also be achieved by using a safe temp-file function. This will ensure that temporary files will not be created in predictable places.
More Creation of Temporary File With Insecure Permissions vulnerabilities (CWE-378)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Technical write-ups (may include proof of concept)
- huntr.com/bounties/648dc30b-76c7-4433-86b8-f43d926fd8d6Exploit, Third Party Advisory
Other vulnerabilities in mlflow/mlflow
- 8.1 High severity
- 7.7 High severity
- 9.0 Critical severity
- 9.6 Critical severity
- 8.6 High severity
- 7.5 High severity
Recent Creation of Temporary File With Insecure Permissions vulnerabilities
- 7.8 High severity
- 7.3 High severity
- 7.4 High severity
- 7.8 High severity
- 8.8 High severity
- 8.8 High severity
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