Answer in brief
CVE-2026-55841 records a High severity (CVSS 7.5) vulnerability in Graylog: Fortigate syslog message parser can be exploited to modify or delete fields from the original message. The current sources do not mark it as known exploited. The current feed maps Graylog2/graylog2-server (generic), org.graylog2:graylog2-server (maven), org.graylog2:graylog2-server (maven), org.graylog2:graylog2-server (maven). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Graylog2/graylog2-server (generic), org.graylog2:graylog2-server (maven), org.graylog2:graylog2-server (maven), org.graylog2:graylog2-server (maven). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Graylog2/graylog2-servergeneric | < 6.3.12 || >= 7.0.0-alpha.1, < 7.0.7 || >= 7.1.0-alpha.1, < 7.1.2 | Not reported |
| org.graylog2:graylog2-servermaven | <6.3.12 | 6.3.12 |
| org.graylog2:graylog2-servermaven | >=7.0.0,<7.0.7 | 7.0.7 |
| org.graylog2:graylog2-servermaven | >=7.1.0,<7.1.2 | 7.1.2 |
Published upstream
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 28, 2026
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.
Quoted source text, attributed separately from HOL analysis.