CVE-2026-12243 nltk: Arbitrary File Read via Path Traversal in nltk.data.load() through Percent-Encoded Sequences
Not scored
Published
Updated
Check this codebase for CVE-2026-12243 and fix it if it is affected.
What it is: CVE-2026-12243 is a vulnerability in nltk, published on 30 Jun 2026.
Exploitation: There is no known exploitation of CVE-2026-12243 in the wild and no public exploit code.
Affected packages and fixed versions:
- nltk (PyPI): affected all versions up to 3.9.4; no fix listed
- nltk (PyPI): affected all versions; fixed in 3.10.0
- nltk (PyPI): affected all versions; fixed in 3.10.0
Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.
Reference: https://insights.sbomify.com/CVE-2026-12243/ (Markdown: https://insights.sbomify.com/CVE-2026-12243/index.md)
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-12243?
CVE-2026-12243 is a vulnerability in nltk, published on 30 Jun 2026.
Official description
This CVE ID has been rejected or withdrawn by its CVE Numbering Authority.
Which versions are affected by CVE-2026-12243?
3 open source packages ship an affected version, including nltk.
| Package | Affected | Fixed in |
|---|---|---|
nltk PyPI | All versions to 3.9.4 | None |
nltk PyPI | All versions | 3.10.0 |
nltk PyPI | All versions | 3.10.0 |
How do I fix CVE-2026-12243?
Upgrade nltk to 3.10.0 or later.
Is CVE-2026-12243 being exploited?
There is no known exploitation of CVE-2026-12243 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as ECHO-e9a7-921d-59ae, GHSA-m42h-3232-vpv3, MINI-6f5r-h3p9-442v, PYSEC-2026-597, UBUNTU-CVE-2026-12243.