virtualenv writes prompt values into pyvenv.cfg without sanitizing line boundaries, allowing configuration injection

Summary pyvenv.cfg is a line-based format with no escape syntax. PyEnvCfg.write wrote values verbatim, while PyEnvCfg.readvalues parses the file with str.splitlines. A value containing a line boundary therefore became additional configuration lines, and because reading is last-wins, the injected...

PYSEC-2026-4012 virtualenv writes prompt values into pyvenv.cfg without sanitizing line boundaries, allowing configuration injection

pyvenv.cfg is a line-based format with no escape syntax. PyEnvCfg.write wrote values verbatim, while PyEnvCfg.readvalues parses the file with str.splitlines. A value containing a line boundary therefore became additional configuration lines, and because reading is last-wins, the injected keys...