virtualenv writes prompt values into pyvenv.cfg without sanitizing line boundaries, allowing configuration injection
Affects virtualenvSource GCVE Database
Not known to be exploited · CVSS 5.8 Medium : upgrade to 21.7.11 when convenient.
Data as of 30 Oct 2026, 06:59 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 3% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 21.7.11
CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:L/VI:H/VA:L/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 29 Sep 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 29 Oct 2026.
What to do
Upgrade virtualenv to 21.7.11.
Patches and advisories
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewvirtualenvpkg:brew/virtualenvOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
virtualenv is a tool for creating isolated virtual python environments. Prior to 21.7.11, PyEnvCfg.write() writes prompt values verbatim to the line-oriented pyvenv.cfg format while PyEnvCfg._read_values() parses the file with str.splitlines() and accepts the last value for duplicate keys. An attacker who influences --prompt, VIRTUALENV_PROMPT, or configuration input can insert a recognized line boundary and additional keys, including home, causing consumers to use an attacker-selected base interpreter or corrupted environment metadata. The security impact requires prompt input from outside the operator's trust boundary; directly supplied prompt content primarily corrupts the operator's own environment. This issue is fixed in version 21.7.11.
References
- github.com/pypa/virtualenv/releases/tag/21.7.11 (opens in a new tab)
- github.com/CVEProject/cvelistV5/tree/main/cves/2026/102xxx/CVE-2026-102938.json (opens in a new tab)
- github.com/pypa/virtualenv/security/advisories/GHSA-9h9j-4vrj-gf7g (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-102938 (opens in a new tab)
- github.com/pypa/virtualenv/commit/a30f995461043acb6cacbf3a890951563ccf7140 (opens in a new tab)
- github.com/pypa/virtualenv/pull/3247 (opens in a new tab)