Graylog CVE-2026-55841
HIGH
GHSA-gqr6-r77p-c2pj
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Syslog is unauthenticated by protocol (PR:N, AV:N); message-discard capability warrants A:L over the vendor's A:N.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
Lifecycle Timeline
4Blast Radius
ecosystem impact- 2 maven packages depend on org.graylog2:graylog2-server (2 direct, 0 indirect)
Ecosystem-wide dependent count for version 7.0.0.
DescriptionCVE.org
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.
AnalysisAI
Log-record tampering in Graylog's FortiGate syslog parser enables unauthenticated network senders to overwrite or erase critical security-log fields - including srcip, dstip, date, time, and tz - or cause entire log messages to be silently discarded, creating a viable log-evasion primitive. Affected are Graylog Server versions prior to 6.3.12, 7.0.7, and 7.1.2 (all branches), and Graylog Forwarder prior to version 7.3, on any deployment ingesting FortiGate key-value syslog. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires network access to a Graylog Syslog input port (typically UDP/514 or TCP/514) on a Graylog Server or Forwarder instance running an affected version. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | CVSS 7.5 with AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N characterizes this as high-severity, network-exploitable with no authentication barrier - consistent with the description's explicit 'unauthenticated network sender' phrasing. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade Graylog Server to version 6.3.12, 7.0.7, or 7.1.2 (select the release matching your current branch), and upgrade Graylog Forwarder to version 7.3 or later. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: identify all Graylog Server deployments running versions prior to 6.3.12 (6.x branch), 7.0.7 (7.0 branch), or 7.1.2 (7.1 branch) and all Graylog Forwarder instances prior to version 7.3; audit syslog listener network exposure and implement temporary firewall rules restricting FortiGate syslog inputs to known-trusted internal source subnets only. …
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External POC / Exploit Code
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