The CGIHTTPServer module in Python 2.7.5 and 3.3.4 does not properly handle URLs in which URL encoding is used for path separators, which allows remote attackers to read script source code or conduct directory traversal attacks and execute unintended code via a crafted character sequence, as demonstrated by a %2f separator.
Severity
CVSS 3.1
9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
24% chance of exploitation in the next 30 days; higher than 97% of CVEs (scores of 2026-10-31)