GHSA-GQR6-R77P-C2PJ

Vulnerability from github – Published: 2026-08-28 22:13 – Updated: 2026-08-28 22:13
VLAI
Summary
Fortigate syslog message parser can be exploited to modify or delete fields from the original message
Details

Impact

A security issue has been identified in Graylog affecting the parsing of syslog messages that use a key-value format, such as those generated by Fortigate devices.

The vulnerability allows attackers to overwrite individual message fields, or to produce invalid messages which Graylog will discard. This effectively enables log evasion techniques to obscure malicious activity.

Patches

The issue has been fixed in the following Graylog versions: 6.3.12, 7.0.7, 7.1.2. Users should upgrade to one of these versions or above to remediate the vulnerability.

Graylog Cloud has already been patched.

Workarounds

There are no feasible workarounds for this issue. Upgrading to a patched version is recommended.

To find potentially discarded messages due to parsing errors, customers of Graylog Enterprise or Security can check the Indexing and Processing Failures Index^1.

Credits

Thanks to Jose Luis González, from Fundación Sarenet, with additional analysis by Borja Marcos from Sarenet.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.graylog2:graylog2-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.3.12"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.graylog2:graylog2-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "7.0.0"
            },
            {
              "fixed": "7.0.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.graylog2:graylog2-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "7.1.0"
            },
            {
              "fixed": "7.1.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55841"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-138"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-28T22:13:00Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Impact\n\nA security issue has been identified in Graylog affecting the parsing of syslog messages that use a key-value format, such as those generated by Fortigate devices.\n\nThe vulnerability allows attackers to overwrite individual message fields, or to produce invalid messages which Graylog will discard. This effectively enables log evasion techniques to obscure malicious activity.\n\n### Patches\n\nThe issue has been fixed in the following Graylog versions: `6.3.12`, `7.0.7`, `7.1.2`. Users should upgrade to one of these versions or above to remediate the vulnerability.\n\nGraylog Cloud has already been patched.\n\n### Workarounds\n\nThere are no feasible workarounds for this issue. Upgrading to a patched version is recommended.\n\nTo find potentially discarded messages due to parsing errors, customers of Graylog Enterprise or Security can check the Indexing and Processing Failures Index[^1]. \n\n### Credits\n\nThanks to Jose Luis Gonz\u00e1lez, from Fundaci\u00f3n Sarenet, with additional analysis by Borja Marcos from Sarenet. \n\n\n[^1]: https://go2docs.graylog.org/current/getting_in_log_data/indexer_and_processing_failures.html",
  "id": "GHSA-gqr6-r77p-c2pj",
  "modified": "2026-08-28T22:13:00Z",
  "published": "2026-08-28T22:13:00Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Graylog2/graylog2-server/security/advisories/GHSA-gqr6-r77p-c2pj"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Graylog2/graylog2-server/pull/26050"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Graylog2/graylog2-server/pull/26056"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Graylog2/graylog2-server/pull/26057"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Graylog2/graylog2-server/pull/26059"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Graylog2/graylog2-server/commit/793df6e8202ea55c15a762e47a2a8a775961dd3f"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Graylog2/graylog2-server/commit/85dc699d6319aea433583dc239077a3a799c8627"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Graylog2/graylog2-server/commit/d5051e604c962ef3d4e5e8e434d0ff4907d2140d"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Graylog2/graylog2-server/commit/dde76d7432c469887d9a95c208083c5f0f73c70d"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Graylog2/graylog2-server"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Fortigate syslog message parser can be exploited to modify or delete fields from the original message"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.