CVE-2026-55841: GRAYLOG2 GRAYLOG2-Server

High severity, CVSS 7.5. EPSS: 0.6% chance of exploitation in the next 30 days.

Graylog is a free and open log management platform. Prior to Graylog Server versions 6.3.12, 7.0.7, and 7.1.2 and Graylog Forwarder version 7.3, the FortiGate key-value syslog parser in graylog2-server/src/main/java/org/graylog2/inputs/codecs/GLFortiGateSyslogEvent.java and graylog2-server/src/main/java/org/graylog2/inputs/codecs/SyslogCodec.java mishandles field-like text inside quoted values. GLFortiGateSyslogEvent.getFields() uses KV_PATTERN and QUOTED_KV_PATTERN, while SyslogCodec.parse() invokes the FortiGateSyslogEvent parser; crafted values containing = or backslash-escaped quotes can cause embedded keys such as srcip, dstip, date, time, and tz to remove or overwrite original top-level fields or produce an invalid message that Graylog discards. An unauthenticated network sender who can submit syslog messages can therefore manipulate security-log fields or evade logging to obscure malicious activity. This issue is fixed in Graylog Server versions 6.3.12, 7.0.7, and 7.1.2 and Graylog Forwarder version 7.3.

Affected products

• GRAYLOG2 GRAYLOG2-Server: before 6.3.12 (fixed in 6.3.12); from 7.0.0-alpha.1, before 7.0.7 (fixed in 7.0.7); from 7.1.0-alpha.1, before 7.1.2 (fixed in 7.1.2)

Published 2026-08-28. Last modified 2026-09-09.