flux2: Improper Limitation of a Pathname to a Restricted Directory
CVE-2022-36035 is a high-severity improper limitation of a pathname to a restricted directory vulnerability in flux2 from Fluxcd, 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. Affected flux2 versions: < 0.32.0, >= 0.21.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.32% 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
- Check which version of flux2 you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
Affected products and versions
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 | 7.7 | High | CNA (github.com) |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
Flux is a tool for keeping Kubernetes clusters in sync with sources of configuration (like Git repositories), and automating updates to configuration when there is new code to deploy. Flux CLI allows users to deploy Flux components into a Kubernetes cluster via command-line. The vulnerability allows other applications to replace the Flux deployment information with arbitrary content which is deployed into the target Kubernetes cluster instead. The vulnerability is due to the improper handling of user-supplied input, which results in a path traversal that can be controlled by the attacker. Users sharing the same shell between other applications and the Flux CLI commands could be affected by this vulnerability. In some scenarios no errors may be presented, which may cause end users not to realize that something is amiss. A safe workaround is to execute Flux CLI in ephemeral and isolated shell environments, which can ensure no persistent values exist from previous processes. However, upgrading to the latest version of the CLI is still the recommended mitigation strategy.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Limitation of a Pathname to a Restricted Directory
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
How developers prevent this class of flaw
- For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
- Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.
More Improper Limitation of a Pathname to a Restricted Directory vulnerabilities (CWE-22)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- github.com/fluxcd/flux2/security/advisories/GHSA-xwf3-6rgv-939rMitigation, Third Party Advisory
Patches and release notes
- github.com/fluxcd/flux2/releases/tag/v0.32.0Release Notes, Third Party Advisory
Other vulnerabilities in flux2
- 7.5 High severity
- 8.8 High severity
- 9.9 Critical severity
Recent Improper Limitation of a Pathname to a Restricted Directory vulnerabilities
- 7.8 High severity
- 7.5 High severity
- 7.5 High severity
- 7.2 High severity
- 7.8 High severity
- 7.8 High severity
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