Advisory details:
gitlab / pypi/nltk/CVE-2026-12075
| Advisory ID | gitlab/pypi/nltk/CVE-2026-12075 |
| Aliases |
CVE-2026-12075
GHSA-qvv7-cg9c-w4x3 |
| Summary | Natural Language Toolkit (NLTK): DNS-rebinding SSRF filter bypass in nltk.pathsec.urlopen (nltk.download / nltk.data.load) defeats ENFORCE mode `nltk.pathsec` provides an SSRF filter that NLTK documents as a security control, blocking loopback, private, link-local, and multicast ranges (including obfuscated forms) and recommending strict `ENFORCE` mode for security-sensitive environments. The filter is bypassable by DNS rebinding: `validate_network_url()` resolves the hostname and checks the resulting IP, but the actual HTTP connection re-resolves the hostname independently at connect time and connects to that second result. The validated IP is never the one connected to. An attacker controlling DNS for a hostname (a TTL-0 rebinding record) returns a public IP for the validation lookup and an internal/loopback IP for the connection lookup, defeating the filter even under `nltk.pathsec.ENFORCE = True`. |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 0.0 |
| Risk | |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| System | Score | Found at |
|---|---|---|
| cvssv3.1 | https://gitlab.com/gitlab-org/advisories-community/-/blob/main/pypi/nltk/CVE-2026-12075.yml |
| Reference id | Reference type | URL |
|---|---|---|
| https://github.com/advisories/GHSA-qvv7-cg9c-w4x3 | ||
| https://github.com/nltk/nltk/security/advisories/GHSA-qvv7-cg9c-w4x3 | ||
| https://nvd.nist.gov/vuln/detail/CVE-2026-12075 |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
There are no SSVC decisions available.