CVE-2021-32921

Severity: medium (CVSS 5.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-05-13 · updated 2026-06-17
Weakness: CWE-362

Description

An issue was discovered in Prosody before 0.11.9. It does not use a constant-time algorithm for comparing certain secret strings when running under Lua 5.2 or later. This can potentially be used in a timing attack to reveal the contents of secret strings to an attacker.

Affected products

Debian Linux: 9.0
Fedoraproject Fedora: 32, 33, 34
Prosody: before 0.11.9 — fixed in 0.11.9

How to fix

Upgrade to a fixed version: Prosody 0.11.9. Check the vendor advisory for mitigations.

References

http://www.openwall.com/lists/oss-security/2021/05/13/1
http://www.openwall.com/lists/oss-security/2021/05/14/2
https://blog.prosody.im/prosody-0.11.9-released/
https://lists.debian.org/debian-lts-announce/2021/06/msg00016.html
https://lists.debian.org/debian-lts-announce/2021/06/msg00018.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6MFFBZWXKPZEVZNQSVJNCUE7WRF3T7DG/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GUN63AHEWB2WRROJHU3BVJRWLONCT2B7/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LWJ2DG2DFJOEFEWOUN26IMYYWGSA2ZEE/
https://security.gentoo.org/glsa/202105-15
https://www.debian.org/security/2021/dsa-4916
http://www.openwall.com/lists/oss-security/2021/05/13/1
http://www.openwall.com/lists/oss-security/2021/05/14/2

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