CVE-2026-71513
NLTK 3.10.0 through 3.10.2 Remote Code Execution via AllowlistUnpickler Dotted-Name Bypass
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Passive
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
NLTK 3.10.0 through 3.10.2 Remote Code Execution via AllowlistUnpickler Dotted-Name Bypass
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
- Record
CVE-2026-71513- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 8.8 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - Weakness
- CWE-502
- Updated
- 2026-11-02
EUVDEUVD-2026-64296
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
- Record
EUVD-2026-64296- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-5gh2-94qg-qppq
NLTK AllowlistUnpickler dotted-name validation bypass allows remote code execution
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
- Record
GHSA-5gh2-94qg-qppq- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 8.8 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - Weakness
- CWE-502
- Updated
- 2026-11-02
NVD
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
- Record
CVE-2026-71513- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/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 - CVSS 3.1
- 8.8 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - Weakness
- CWE-502
- Updated
- 2026-11-02
OSV
NLTK 3.10.0 through 3.10.2 Remote Code Execution via AllowlistUnpickler Dotted-Name Bypass
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
- Record
CVE-2026-71513- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N - Weakness
- CWE-502
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-71513
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
- Record
DEBIAN-CVE-2026-71513- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/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 - Updated
- 2026-11-02
Show 5 moreShow less
OSVGHSA-5gh2-94qg-qppq
NLTK AllowlistUnpickler dotted-name validation bypass allows remote code execution
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
- Record
GHSA-5gh2-94qg-qppq- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 8.8 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - Weakness
- CWE-502
- Updated
- 2026-11-02
OSVPYSEC-2026-3867
NLTK AllowlistUnpickler dotted-name validation bypass allows remote code execution
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
- Record
PYSEC-2026-3867- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 8.8 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-71513
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
- Record
UBUNTU-CVE-2026-71513- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 8.8 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - CVSS 3.1
- 8.8 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVMGASA-2026-0340 No score
Updated python-nltk packages fix security vulnerabilities
Updated packages fix security vulnerabilities. Please see the links.
- Record
MGASA-2026-0340- Updated
- 2026-11-02
OSVopenSUSE-SU-2026:11587-1 No score
python313-nltk-3.10.3-1.1 on GA media
These are all security issues fixed in the python313-nltk-3.10.3-1.1 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2026:11587-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
nltkPyPI |
3.10.0 up to 3.10.3 | 3.10.3 |
nltkDebian:12 |
All versions, plus listed versions 3.10.0-13.10.1-13.10.3-13.8-13.8.1-1 Show 4 moreShow less3.9.1-13.9.1-23.9.2-13.9.3-1 |
None known |
nltkDebian:13 |
All versions, plus listed versions 3.10.0-13.10.1-13.10.3-13.9.1-23.9.2-13.9.3-1 |
None known |
nltkDebian:14 |
before 3.10.3-1, plus listed versions 3.10.0-13.10.1-13.9.1-23.9.2-13.9.3-1 |
3.10.3-1 |
nltkPyPI |
3.10.0 up to 3.10.3, plus listed versions 3.10.13.10.2 |
3.10.3 |
python-nltkMageia:10 From an advisory covering 18 CVEs |
before 3.10.3-1.mga10 | 3.10.3-1.mga10 |
python-nltkMageia:9 From an advisory covering 18 CVEs |
before 3.10.3-1.mga9 | 3.10.3-1.mga9 |
nltkUbuntu:Pro:14.04:LTS |
All versions, plus listed versions 2.0~b9-0ubuntu42.0~b9-0ubuntu4.1~esm22.0~b9-0ubuntu4.1~esm42.0~b9-0ubuntu4.1~esm52.0~b9-0ubuntu4.1~esm6 |
None known |
nltkUbuntu:Pro:16.04:LTS |
All versions, plus listed versions 3.0.4-13.0.5-13.1-13.1-1ubuntu0.13.1-1ubuntu0.1+esm13.1-1ubuntu0.1+esm23.1-1ubuntu0.1+esm33.1-1ubuntu0.1+esm4 |
None known |
nltkUbuntu:Pro:18.04:LTS |
All versions, plus listed versions 3.2.4-13.2.5-13.2.5-1ubuntu0.13.2.5-1ubuntu0.1+esm13.2.5-1ubuntu0.1+esm23.2.5-1ubuntu0.1+esm33.2.5-1ubuntu0.1+esm4 |
None known |
Show 6 moreShow less
| Package | Affected | Fixed |
|---|---|---|
nltkUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 3.4.5-13.4.5-23.4.5-2ubuntu0.1~esm13.4.5-2ubuntu0.1~esm23.4.5-2ubuntu0.1~esm33.4.5-2ubuntu0.1~esm4 |
None known |
nltkUbuntu:Pro:22.04:LTS |
All versions, plus listed versions 3.5-13.6.5-13.6.7-13.7-13.7-1ubuntu0.1~esm13.7-1ubuntu0.1~esm2 |
None known |
nltkUbuntu:Pro:24.04:LTS |
All versions, plus listed versions 3.8.1-13.8.1-1ubuntu0.1~esm13.8.1-1ubuntu0.1~esm2 |
None known |
nltkUbuntu:26.10 |
All versions, plus listed versions 3.9.2-13.9.3-13.10.0-13.10.1-13.10.3-1 |
None known |
nltkUbuntu:Pro:26.04:LTS |
All versions, plus listed versions 3.9.1-23.9.1-2build13.9.2-13.9.2-1ubuntu0.1~esm13.9.2-1ubuntu0.1~esm2 |
None known |
python-nltkopenSUSE:Tumbleweed From an advisory covering 2 CVEs |
before 3.10.3-1.1 | 3.10.3-1.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-71513 is a high vulnerability (CVSS 8.7) in Nltk, published August 22, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.10%, the 65th percentile. Fixed in nltk 3.10.3.
References
github.com/nltk/nltk/commit/c3e37113742a1ebeeb4f2ca58941f320f98805ea
vulncheck.com/advisories/nltk-through-remote-code-execution-via-allowlistunpickler-dotted-name-bypass
nvd.nist.gov/vuln/detail/CVE-2026-71513
Show 13 moreShow less
security-tracker.debian.org/tracker/CVE-2026-71513
advisories.mageia.org/MGASA-2026-0340.html
bugs.mageia.org/show_bug.cgi?id=36186
pypi.org/project/nltk
ubuntu.com/security/CVE-2026-71513
cve.org/CVERecord?id=CVE-2026-71513
suse.com/security/cve/CVE-2026-12252