# CVE-2026-62388: NLTK before 3.10.0 Insecure Default Configuration in pathsec.py

> Attackers can bypass path traversal and deserialization protections in NLTK because security checks are disabled by default, requiring an upgrade to enforce them.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Aug 2026
- **Updated:** 29 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-62388, ECHO-7cc1-59c5-b855, GHSA-p3m8-78j2-g5p3, MINI-9353-p28q-mfcp, PYSEC-2026-3722, UBUNTU-CVE-2026-62388

## What is CVE-2026-62388?

CVE-2026-62388 is a high-severity vulnerability in nltk, published on 22 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

NLTK versions before 3.10.0 default to ENFORCE=False in pathsec.py, causing all security validation functions to emit warnings instead of raising exceptions. Attackers can bypass path traversal and pickle deserialization protections by exploiting the disabled security controls that are only active when manually enabled.

Weakness: CWE-1188 (Initialization of a Resource with an Insecure Default)

## Which versions are affected by CVE-2026-62388?

3 open source packages ship an affected version, including nltk. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nltk` | PyPI | All versions | 3.10.0 |
| `nltk` | PyPI | All versions | 3.10.0 |
| `nltk` | PyPI | All versions | 3.10.0 |

Products: Nltk Nltk.

## How do I fix CVE-2026-62388?

Upgrade nltk to 3.10.0 or later.

## Is CVE-2026-62388 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-62388 exists.

## Other vulnerabilities in nltk

- [CVE-2026-0848](https://insights.sbomify.com/CVE-2026-0848/): Arbitrary Code Execution in NLTK StanfordSegmenter via Untrusted JAR Loading (critical 10.0)
- [CVE-2025-14009](https://insights.sbomify.com/CVE-2025-14009/): Zip Slip Vulnerability in nltk/nltk Leading to Remote Code Execution (critical 10.0)
- [CVE-2026-78683](https://insights.sbomify.com/CVE-2026-78683/): NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization (critical 9.4)
- [CVE-2026-79657](https://insights.sbomify.com/CVE-2026-79657/): NLTK before 3.10.3 Remote Code Execution via Unsafe Pickle Deserialization (critical 9.3)
- [CVE-2026-79675](https://insights.sbomify.com/CVE-2026-79675/): NLTK before 3.10.3 JVM Argument Injection via Per-Call Options (critical 9.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-62388 and fix it if it is affected.

What it is: CVE-2026-62388 is a high-severity vulnerability in nltk, published on 22 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-62388 exists.

Affected packages and fixed versions:
- nltk (PyPI): affected all versions; fixed in 3.10.0
- 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-2026-62388/ (Markdown: https://insights.sbomify.com/CVE-2026-62388/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-62388
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-62388
- OSV: https://osv.dev/vulnerability/CVE-2026-62388

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-62388/
Summaries are generated and may contain mistakes; the official description above is the record.