CVE catalog
CVE-2026-78683
NLTK before 3.10.0 (affected versions <=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py). The method calls pickle_
- Severity
- Critical · CVSS 9.6
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H - Published
- Updated
- Source
- [NVD] · [CVE record]
- EPSS
- 0.51% · Oct 25, 2026
NLTK before 3.10.0 (affected versions <=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py). The method calls pickle_load() with the default restricted=False, routing deserialization through WarningUnpickler, which does not override find_class() and therefore permits arbitrary class resolution. When an application loads an attacker-crafted model file, embedded pickle gadget chains execute arbitrary Python code with the privileges of the user running the application. NLTK provides a RestrictedUnpickler for safe deserialization, but it is not used by production code paths. Fixed in 3.10.0.
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-2026-78683 | Not reported |
| PyPI | nltk | PyPI | Not reported | 3.10.0 | Not reported | PYSEC-2026-3734 | Not reported |
| Pip | nltk | pip | Not reported | 3.10.0 | Not reported | GHSA-RHP5-R9X4-F5G2 | 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
nvd · nltk · debian · bookworm; nvd · nltk · debian · 12
3.8-1· all · bookwormAffected
nvd · nltk · debian · bookworm; nvd · nltk · debian · 12
[Debian 13 (Trixie)]
- [python3-nltk]Affected
Source package: [nltk]
Details (2)
3.9.1-2· all · trixieAffected
nvd · nltk · debian · 13
3.9.1-2· all · trixieAffected
nvd · nltk · debian · 13
Observed:
References
- [https://github.com/advisories/GHSA-rhp5-r9x4-f5g2]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-78683]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-78683]
- [https://security-tracker.debian.org/tracker/CVE-2026-78683]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-78683.json]
[Debian Security Tracker] · [FIRST EPSS] · [GitHub Advisory Database] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX]