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CVE-2025-71408

NLTK < 3.9.3 Eval Injection via collocations.py Command-Line Arguments

8.5 HighFix available

NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the main block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

0.27%Up 0.1 points since Jul 25, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.5

NLTK < 3.9.3 Eval Injection via collocations.py Command-Line Arguments

NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the main block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.

Record
CVE-2025-71408
CVSS 4.0
8.5 HighCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
7.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-95
Updated
2026-11-02
EUVDEUVD-2025-210509 8.5

NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the main block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.

Record
EUVD-2025-210509
CVSS 4.0
8.5 HighCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-848c-c2cx-j7qx 8.5

NLTK vulnerable to Eval Injection via collocations CLI arguments

NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the main block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.

Record
GHSA-848c-c2cx-j7qx
CVSS 4.0
8.5 HighCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
7.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-95
Updated
2026-11-02
NVD 8.5

NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the main block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.

Record
CVE-2025-71408
CVSS 4.0
8.5 HighCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/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
7.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-95
Updated
2026-11-02
OSV 8.5

NLTK < 3.9.3 Eval Injection via collocations.py Command-Line Arguments

NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the main block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.

Record
CVE-2025-71408
CVSS 4.0
8.5 HighCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-95
Updated
2026-11-02
OSVDEBIAN-CVE-2025-71408 8.5

NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the main block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.

Record
DEBIAN-CVE-2025-71408
CVSS 4.0
8.5 HighCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/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
OSVGHSA-848c-c2cx-j7qx 8.5

NLTK vulnerable to Eval Injection via collocations CLI arguments

NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the main block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.

Record
GHSA-848c-c2cx-j7qx
CVSS 4.0
8.5 HighCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
7.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-95
Updated
2026-11-02
OSVPYSEC-2026-3657 8.5

NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the main block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.

Record
PYSEC-2026-3657
CVSS 4.0
8.5 HighCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/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
OSVUBUNTU-CVE-2025-71408 8.5

NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the main block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.

Record
UBUNTU-CVE-2025-71408
CVSS 4.0
8.5 HighCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
7.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
nltk
PyPI
before 3.9.3
3.9.3
nltk
Debian:12
All versions, plus listed versions
3.10.0-13.10.1-13.10.3-13.8-13.8.1-1
Show 4 moreShow less
3.9.1-13.9.1-23.9.2-13.9.3-1
None known
nltk
Debian: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
nltk
Debian:14
before 3.9.3-1, plus listed versions
3.9.1-23.9.2-1
3.9.3-1
nltk
PyPI
before 3.9.3, plus listed versions
0.80.90.9.30.9.40.9.5
Show 45 moreShow less
0.9.60.9.70.9.80.9.92.0.12.0.1rc12.0.1rc2-git2.0.1rc32.0.1rc42.0.22.0.32.0.42.0.52.0b42.0b52.0b62.0b72.0b82.0b93.0.03.0.0b13.0.0b23.0.13.0.23.0.33.0.43.0.53.13.23.2.13.2.23.2.33.2.43.2.53.33.43.4.13.4.23.4.33.4.43.4.53.53.5b13.63.6.1
3.9.3
nltk
Ubuntu: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
nltk
Ubuntu: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
nltk
Ubuntu: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
nltk
Ubuntu: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
nltk
Ubuntu: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
nltk
Ubuntu: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
nltk
Ubuntu: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

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-71408 is a high vulnerability (CVSS 8.5) in Nltk, published July 24, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.27%, the 18th percentile. Fixed in nltk 3.9.3.

References

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Left out here: 13 versions. The JSON record has them.

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