CVE-2026-55841
Graylog: Fortigate syslog message parser can be exploited to modify or delete fields from the original message
- State
- Published
- Severity
- 7.5 High
- Published
- Aug 28, 2026
- Updated
- Sep 1, 2026
- Reserved
- Jun 17, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N | GitHub_M |
Weaknesses
- CWE-138 Improper Neutralization of Special Elements
Affected Products
| Product | Versions |
|---|---|
graylog2-serverGraylog2 |
|
References
- https://github.com/Graylog2/graylog2-server/security/advisories/GHSA-gqr6-r77p-c2pj
- https://github.com/Graylog2/graylog2-server/pull/26050
- https://github.com/Graylog2/graylog2-server/pull/26056
- https://github.com/Graylog2/graylog2-server/pull/26057
- https://github.com/Graylog2/graylog2-server/pull/26059
- https://github.com/Graylog2/graylog2-server/commit/793df6e8202ea55c15a762e47a2a8a775961dd3f
- https://github.com/Graylog2/graylog2-server/commit/85dc699d6319aea433583dc239077a3a799c8627
- https://github.com/Graylog2/graylog2-server/commit/d5051e604c962ef3d4e5e8e434d0ff4907d2140d
- https://github.com/Graylog2/graylog2-server/commit/dde76d7432c469887d9a95c208083c5f0f73c70d
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