VulnerabilityPublished 13 Aug 2026Updated 17 Sep 2026

CVE-2026-12072: Gptline · Natural Language Toolkit (NLTK): Path Traversal in NKJPCorpusReader leads to Arbitrary File Read and bypasses the nltk.pathsec sandbox (ENFORCE=True)

Affects gptlineSource GCVE Database

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Not known to be exploited · CVSS 7.5 High : upgrade to 1.0.8_22 soon.

Data as of 18 Sep 2026, 02:18 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 3.10.0, 1.0.8_22

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade gptline to 1.0.8_22; nltk to 3.10.0.

Affected software

Product	Affected	Fixed in
PyPInltk	Affected <3.10.0	Fixed in 3.10.0
Homebrewgptline`pkg:brew/gptline`Other threats	Affected >=1.0.8 <1.0.8_22	Fixed in 1.0.8_22

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available for this vulnerability. Users should upgrade to a fixed version of NLTK where NKJPCorpusReader properly validates and normalizes file paths and uses the protected pathsec APIs to enforce sandboxing. Until patched, do not use NKJPCorpusReader with untrusted input for the fileids argument, and avoid enabling ENFORCE=True as it does not mitigate this issue. Check the official NLTK advisories or repository for the specific patched versions and upgrade accordingly.

Description

A path traversal vulnerability in the Natural Language Toolkit (NLTK) component NKJPCorpusReader allows an attacker to read arbitrary files outside the intended corpus root directory. This occurs because NKJPCorpusReader constructs file paths via unsafe string concatenation and uses the builtin open() function directly, bypassing NLTK's pathsec sandbox protections even when strict enforcement mode (ENFORCE=True) is enabled. The vulnerability was confirmed in NLTK version 3.9.4 and the current development branch. An attacker controlling the fileids argument can exploit this to read sensitive files outside the corpus root.

Impact

An unauthenticated attacker who can influence the fileids argument to NKJPCorpusReader's public read methods can read arbitrary files on the filesystem outside the intended corpus root directory. This can lead to disclosure of sensitive information such as secret keys or configuration files. The vulnerability bypasses NLTK's pathsec sandbox protections, including the strict ENFORCE=True mode recommended for multi-tenant or web deployments, meaning existing sandbox enforcement does not prevent exploitation.

Summary

The NKJPCorpusReader in NLTK suffers from a path traversal vulnerability (CWE-22) due to unsafe path construction and direct use of the builtin open() function without invoking NLTK's pathsec validation. The add_root() method concatenates the root and fileid strings without normalization or containment checks, allowing '..' sequences to escape the corpus root. The header() method appends a fixed suffix and opens the file using builtin open(), bypassing the pathsec sandbox even when ENFORCE=True. This leads to arbitrary file read outside the corpus root. The issue was demonstrated with a proof-of-concept against NLTK 3.9.4, showing disclosure of sensitive file content outside the corpus root. The vulnerability has a CVSS 3.1 score of 7.5 (high severity) with network attack vector, low complexity, no privileges required, no user interaction, and high confidentiality impact.

CWE-22Improper Limitation of a Pathname to a Restricted Directory (Path Traversal) (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #6OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
Implementation · Input Validation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174).
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.3.1 (opens in a new tab)
Attack patterns
Path Traversal (opens in a new tab)
Using Slashes and URL Encoding Combined to Bypass Validation Logic (opens in a new tab)
Manipulating Web Input to File System Calls (opens in a new tab)
Using Escaped Slashes in Alternate Encoding (opens in a new tab)
Using Slashes in Alternate Encoding (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 18 Sep 2026, 02:18 UTC

WeaknessesCWE-22

Technical details

References

Community reviews

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