Advisory details:
github_osv / GHSA-p3m8-78j2-g5p3
| Advisory ID | github_osv/GHSA-p3m8-78j2-g5p3 |
| Aliases |
CVE-2026-62388
|
| Summary | NLTK: Default ENFORCE=False Disables All pathsec Security Controls NLTK's pathsec.py security module defaults to ENFORCE=False (line 24), which means all 8 security validation functions only emit RuntimeWarning instead of raising exceptions when violations are detected. The pathsec module was introduced as the fix for CVE-2024-39705 (arbitrary code execution via pickle) and CVE-2026-0846 (path traversal). However, with ENFORCE=False as the default: 1. pathsec.open('/etc/passwd') succeeds (reads the file, emits warning) 2. pathsec.validate_network_url('http://169.254.169.254/...') succeeds (warning only) 3. pickle.loads() via nltk.data.load() proceeds despite unsafe source (warning only) Every security gate follows the same pattern: ```python ENFORCE = os.environ.get('NLTK_PATHSEC_ENFORCE', '').lower() in ('1', 'true', 'yes') def validate_something(path): if is_violation(path): if ENFORCE: raise SecurityError('...') # Only raised when env var is set else: warnings.warn('...', RuntimeWarning) # Default: warning only # Execution continues regardless ``` This means the security remediations for CVE-2024-39705 and CVE-2026-0846 are effectively disabled by default. Any user who installed NLTK 3.9.x expecting the security fixes to be active is still vulnerable unless they manually set NLTK_PATHSEC_ENFORCE=1. PoC: ```python import nltk.pathsec import warnings # Show that ENFORCE is False by default print(f'ENFORCE = {nltk.pathsec.ENFORCE}') # False # Attempt to read /etc/passwd through pathsec -- should be blocked with warnings.catch_warnings(record=True) as w: warnings.simplefilter('always') result = nltk.pathsec.open('/etc/passwd', 'r') print(f'File opened: {result.name}') # /etc/passwd print(f'Warning emitted: {w[0].message}') # RuntimeWarning (not an exception) # Attack succeeds -- file is readable ``` The correct default is fail-secure: ENFORCE should be True unless explicitly disabled. The current default makes the security module opt-in rather than opt-out, defeating its purpose. Suggested fix: Change default to ENFORCE=True. Users who need backwards compatibility can set NLTK_PATHSEC_ENFORCE=0 to explicitly disable. |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 7.8 |
| Risk | 3.9 |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| System | Score | Found at |
|---|---|---|
| cvssv4 | 8.7 | https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-p3m8-78j2-g5p3/GHSA-p3m8-78j2-g5p3.json |
| generic_textual | HIGH |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Attack Requirements (AT) | Privileges Required (PR) | User Interaction (UI) | Vulnerable System Impact Confidentiality (VC) | Vulnerable System Impact Integrity (VI) | Vulnerable System Impact Availability (VA) | Subsequent System Impact Confidentiality (SC) | Subsequent System Impact Integrity (SI) | Subsequent System Impact Availability (SA) |
|---|---|---|---|---|---|---|---|---|---|---|
network adjacent local physical |
low high |
none present |
none low high |
none passive active |
high low none |
high low none |
high low none |
high low none |
high low none |
high low none |
There are no SSVC decisions available.