CVE-2021-36093: DoS attack using PostMaster filters

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-09-06 · updated 2026-06-17
Weakness: CWE-185

Description

It's possible to create an email which can be stuck while being processed by PostMaster filters, causing DoS. This issue affects: OTRS AG ((OTRS)) Community Edition 6.0.x version 6.0.1 and later versions. OTRS AG OTRS 7.0.x version 7.0.28 and prior versions; 8.0.x version 8.0.15 and prior versions.

Affected products

OTRS AG OTRS: from 6.0.1; from 7.0.0 before 7.0.29; from 8.0.0 before 8.0.16 — fixed in 7.0.29, 8.0.16

How to fix

Upgrade to a fixed version: OTRS AG OTRS 7.0.29, 8.0.16. Check the vendor advisory for mitigations.

References

https://otrs.com/release-notes/otrs-security-advisory-2021-16/
https://otrs.com/release-notes/otrs-security-advisory-2021-16/

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