CVE-2026-55841Public exploitNetwork attack vectorHinoki check available

Log field manipulation via quoted-value misparsing

Published Aug 28, 2026 · Updated Aug 28, 2026

Improper input neutralization in affected Graylog Open Server releases allows remote attackers to alter or suppress ingested logs. The FortiGate key-value syslog parser treats key-like text inside quoted values as top-level fields instead of consuming each quoted value as one token. An unauthenticated network sender who can reach a configured syslog input can overwrite attribution fields or make malformed date and time fields cause message discard.

CVSS severity7.5
High
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Improper input neutralization in affected Graylog Open Server releases allows remote attackers to alter or suppress ingested logs. The FortiGate key-value syslog parser treats key-like text inside quoted values as top-level fields instead of consuming each quoted value as one token. An unauthenticated network sender who can reach a configured syslog input can overwrite attribution fields or make malformed date and time fields cause message discard.

The record

CVE
CVE-2026-55841
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
Graylog
Product
Graylog Open Server
Classifications
CWE-138, T1562.006
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 6.3.12
  2. Affected versionversion=>= 7.0.0-alpha.1, < 7.0.7
  3. Affected versionversion=>= 7.1.0-alpha.1, < 7.1.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Graylog · Graylog Open Serverversion=< 6.3.12; version=>= 7.0.0-alpha.1, < 7.0.7; version=>= 7.1.0-alpha.1, < 7.1.2

Published CVSS scores

7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-138Improper Neutralization of Special Elements
T1562.006Indicator Blocking

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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