nltk/nltk: Absolute Path Traversal
CVE-2026-0846 is a high-severity absolute path traversal vulnerability in nltk/nltk from Nltk, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected nltk/nltk versions: latest and earlier. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.59% 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 nltk/nltk you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on huntr.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Nltk | nltk/nltk | latest and earlier | Not stated |
| Red Hat | Red Hat OpenShift AI 2.25 | Not specified in the record | Not stated |
| Red Hat | Red Hat OpenShift AI 3.3 | Not specified in the record | Not stated |
| Red Hat | Lightspeed Core | Not specified in the record | Not stated |
| Red Hat | OpenShift Lightspeed | Not specified in the record | Not stated |
| Red Hat | Red Hat Ansible Automation Platform 2 | Not specified in the record | Not stated |
| Red Hat | Red Hat OpenShift AI (RHOAI) | Not specified in the record | Not stated |
| Nltk | Nltk | 3.9.2 | Not stated |
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
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- 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
- NoneNothing can be modified.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.5 | High | NVD |
| CVSS 3.1 | 7.5 | High | CNA |
| CVSS 3.0 | 8.6 | High | CNA (huntr.dev) |
Official description
A vulnerability in the `filestring()` function of the `nltk.util` module in nltk version 3.9.2 allows arbitrary file read due to improper validation of input paths. The function directly opens files specified by user input without sanitization, enabling attackers to access sensitive system files by providing absolute paths or traversal paths. This vulnerability can be exploited locally or remotely, particularly in scenarios where the function is used in web APIs or other interfaces that accept user-supplied input.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Absolute Path Traversal
The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize absolute path sequences such as /abs/path that can resolve to a location that is outside of that directory.
How developers prevent this class of flaw
- Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
- 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.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other references
Other vulnerabilities in nltk/nltk
- 7.8 High severity
- 7.5 High severity
- 10.0 Critical severity
- 7.5 High severity
- 8.8 High severity
Recent Absolute Path Traversal vulnerabilities
- 7.5 High severity
- 8.2 High severity
- 7.5 High severity
- 9.8 Critical severity
- 8.0 High severity
- 7.1 High severity
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