# CVE-2026-78682: NLTK before 3.10.3 SSRF Protection Bypass via Proxy

> Attackers can bypass SSRF protections in NLTK when a proxy is configured, accessing internal services and installing malicious packages.

- **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:** 25 Aug 2026
- **Updated:** 8 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-78682, ECHO-30ab-58c5-2613, GHSA-6ww7-3frv-cqxh, MINI-wv4q-9vxh-vw8c, PYSEC-2026-3733

## What is CVE-2026-78682?

CVE-2026-78682 is a high-severity server-side request forgery vulnerability in nltk, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

NLTK before 3.10.3 contains a server-side request forgery vulnerability in nltk.pathsec.urlopen (and callers nltk.data.load, nltk.downloader.Downloader.index/download) when an HTTP proxy is configured. pathsec.urlopen validates the requested hostname locally, but proxy-handler inheritance disables the safe HTTP/HTTPS handlers so the actual fetch is performed by the proxy against a destination that is never re-validated. An attacker can supply a validated public URL that the proxy forwards to an internal loopback-only service, allowing disclosure of internal HTTP resources, loading of forged downloader indexes, and installation of attacker-chosen package content.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-78682?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nltk` | PyPI | All versions | 3.10.3 |
| `nltk` | PyPI | All versions | 3.10.3 |
| `nltk` | PyPI | All versions | 3.10.3 |

Products: Nltk Nltk.

## How do I fix CVE-2026-78682?

Upgrade nltk to 3.10.3 or later.

## Is CVE-2026-78682 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-78682 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-2026-78682 and fix it if it is affected.

What it is: CVE-2026-78682 is a high-severity server-side request forgery vulnerability in nltk, published on 25 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-2026-78682 exists.

Affected packages and fixed versions:
- nltk (PyPI): affected all versions; fixed in 3.10.3
- nltk (PyPI): affected all versions; fixed in 3.10.3
- nltk (PyPI): affected all versions; fixed in 3.10.3

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-2026-78682/ (Markdown: https://insights.sbomify.com/CVE-2026-78682/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-78682
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-78682
- OSV: https://osv.dev/vulnerability/CVE-2026-78682

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-78682/
Summaries are generated and may contain mistakes; the official description above is the record.