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CVE-2026-102938VulnerabilityPublished Updated

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

Affects virtualenvSource GCVE Database

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Authoritative record:CVE-2026-102938· Medium 5.8

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

CVSS 4.0 base score
5.8Medium
How severe the flaw is on the 0–10 CVSS scale.
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:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 29 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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.

Affected software

ProductAffectedFixed in
Homebrewvirtualenvpkg:brew/virtualenvOther threatsAffected
  • >=20.4.3 <21.7.11
Fixed in
  • 21.7.11

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

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