CVE-2021-3429: sensitive data exposure in cloud-init logs

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-04-19 · updated 2026-06-17
Weakness: CWE-532

Description

When instructing cloud-init to set a random password for a new user account, versions before 21.2 would write that password to the world-readable log file /var/log/cloud-init-output.log. This could allow a local user to log in as another user.

Affected products

Canonical Ltd. cloud-init: before 21.2 — fixed in 21.2

How to fix

Upgrade to a fixed version: Canonical Ltd. cloud-init 21.2. Check the vendor advisory for mitigations.

References

https://github.com/canonical/cloud-init/commit/b794d426b9ab43ea9d6371477466070d86e10668
https://github.com/canonical/cloud-init/commit/b794d426b9ab43ea9d6371477466070d86e10668

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