Vulnerability · Published Aug 28, 2026 · Assigned by GitHub_M
CVE-2026-55841Graylog: Fortigate syslog message parser can be exploited to modify or delete fields from the original message
High 7.5
In plain English
A high-severity security flaw in graylog2-server from Graylog2. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 51% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Maven | org.graylog2:graylog2-server | 6.3.12 | GHSA-gqr6-r77p-c2pj |
| Maven | org.graylog2:graylog2-server | 7.0.7 | GHSA-gqr6-r77p-c2pj |
| Maven | org.graylog2:graylog2-server | 7.1.2 | GHSA-gqr6-r77p-c2pj |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Graylog2 | graylog2-server | < 6.3.12>= 7.0.0-alpha.1, < 7.0.7>= 7.1.0-alpha.1, < 7.1.2 |
Weakness: CWE-138 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
References
- https://github.com/Graylog2/graylog2-server/security/advisories/GHSA-gqr6-r77p-c2pj x_refsource_CONFIRM
- https://github.com/Graylog2/graylog2-server/pull/26050 x_refsource_MISC
- https://github.com/Graylog2/graylog2-server/pull/26056 x_refsource_MISC
- https://github.com/Graylog2/graylog2-server/pull/26057 x_refsource_MISC
- https://github.com/Graylog2/graylog2-server/pull/26059 x_refsource_MISC
- https://github.com/Graylog2/graylog2-server/commit/793df6e8202ea55c15a762e47a2a8a775961dd3f x_refsource_MISC
- https://github.com/Graylog2/graylog2-server/commit/85dc699d6319aea433583dc239077a3a799c8627 x_refsource_MISC
- https://github.com/Graylog2/graylog2-server/commit/d5051e604c962ef3d4e5e8e434d0ff4907d2140d x_refsource_MISC
- https://github.com/Graylog2/graylog2-server/commit/dde76d7432c469887d9a95c208083c5f0f73c70d x_refsource_MISC