SB2026081130 - Multiple vulnerabilities in Natural Language Toolkit

Description

This security bulletin contains information about 3 vulnerabilities.

1) Link following (CVE-ID: N/A)

CWE-ID: CWE-59 - Improper Link Resolution Before File Access ('Link Following')

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to improper link resolution before file access in FramenetCorpusReader when resolving corpus file paths through symlinks. A remote attacker can place a symlink inside a corpus subdirectory and invoke a normal public API call to disclose sensitive information.

Exploitation requires a tampered or shared corpus directory, and no user interaction is required.

2) Link following (CVE-ID: N/A)

CWE-ID: CWE-59 - Improper Link Resolution Before File Access ('Link Following')

CVSSv4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a local user to disclose sensitive information.

The vulnerability exists due to improper link resolution before file access in IPIPANCorpusReader _get_tag() when processing caller-supplied fileids that reference a symlink within the corpus root. A local user can place a symlinked file in a reachable corpus directory and trigger file reading through channels(), domains(), categories(), or fileids(channels=...) to disclose sensitive information.

Literal ../ traversal in the fileid is still blocked, so the issue is specific to symlink-based access to files outside the corpus root.

3) Inefficient Algorithmic Complexity (CVE-ID: N/A)

CWE-ID: CWE-407 - Inefficient Algorithmic Complexity

CVSSv4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to inefficient algorithmic complexity in XMLCorpusView._read_xml_fragment() when processing attacker-controlled XML corpus files. A remote attacker can supply a malformed XML file to cause a denial of service.

The issue is triggered by quadratic rescanning of the accumulated fragment buffer, and no user interaction is required.

Remediation

Install update from vendor's website.

References

• https://github.com/nltk/nltk/security/advisories/GHSA-f833-7jw8-xwrv
• https://github.com/nltk/nltk/security/advisories/GHSA-3hhw-38pf-pxj6
• https://github.com/nltk/nltk/security/advisories/GHSA-vp2x-qp44-57v7