CVE catalog
CVE-2026-63311
nltk: CVE-2026-63311
- Severity
- Medium · CVSS 6.9
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 0.33% · Oct 25, 2026
NLTK before 3.10.0 (affected versions <= 3.9.4) contains a server-side request forgery (SSRF) vulnerability in the validate_network_url() function in nltk/pathsec.py. The _resolve_hostname() helper catches OSError and ValueError during socket.getaddrinfo() and returns an empty list; when DNS resolution fails, the validation loop executes no IP checks and the function fails open, allowing urlopen() to proceed without validation. An attacker who can trigger DNS resolution failures or use DNS rebinding can bypass SSRF protections and reach restricted network resources, including cloud metadata endpoints (e.g., 169.254.169.254).
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | nltk | sid | 3.10.3-1 | fixed |
| Debian | nltk | forky | 3.10.3-1 | fixed |
| Debian | nltk | trixie | 3.9.1-2 | vulnerable |
| Debian | nltk | bookworm | 3.8-1 | vulnerable |
| Cpe | nltk | Not reported | 3.10.0 | fixed |
| PyPI | nltk | Not reported | 3.10.0 | fixed |
| Pip | nltk | Not reported | 3.10.0 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | nltk | source | sid | 3.10.0-1 | not yet assigned | Not reported | Not reported |
| Debian | nltk | source | forky | 3.10.0-1 | not yet assigned | Not reported | Not reported |
| Debian | nltk | source | trixie | (unfixed) | not yet assigned | Not reported | Not reported |
| Debian | nltk | source | bookworm | (unfixed) | not yet assigned | Not reported | Not reported |
| Cpe | nltk | cpe | Not reported | 3.10.0 | Not reported | NVD-CVE-2026-63311 | Not reported |
| PyPI | nltk | PyPI | Not reported | 3.10.0 | Not reported | PYSEC-2026-3723 | Not reported |
| Pip | nltk | pip | Not reported | 3.10.0 | Not reported | GHSA-3GQM-FCW5-W839 | Not reported |
Notes
[trixie] nltk: Minor issue [bookworm] nltk: Minor issue
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [python3-nltk]Affected
Source package: [nltk]
Details (2)
3.8-1· all · bookwormAffected
dsa · nltk · debian · bookworm
3.8-1· all · bookwormAffected
dsa · nltk · debian · bookworm
Observed:
References
- [https://github.com/advisories/GHSA-3gqm-fcw5-w839]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-63311]
- [https://osv.dev/vulnerability/CVE-2026-63311]
- [https://security-tracker.debian.org/tracker/CVE-2026-63311]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63311.json]
[Debian Security Tracker] · [FIRST EPSS] · [GitHub Advisory Database] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX]