{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "6.3.12"
              },
              {
                "introduced": "7.0.0-alpha.1"
              },
              {
                "fixed": "7.0.7"
              },
              {
                "introduced": "7.1.0-alpha.1"
              },
              {
                "fixed": "7.1.2"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "introduced": "dac42698ecd7e1be0652802e6308c55b0fc5cdca"
            },
            {
              "introduced": "a9355313df2c2106f48684eb47617980ab4d42db"
            },
            {
              "fixed": "fd62097b3ac4d3f18641e973e4823ed9bf663122"
            },
            {
              "fixed": "5cd524ef532ecf6c77fe5efebcd0d2a5143f893c"
            },
            {
              "fixed": "adc626831f3170716845df46ae9237b7e93e1d7d"
            },
            {
              "fixed": "793df6e8202ea55c15a762e47a2a8a775961dd3f"
            },
            {
              "fixed": "85dc699d6319aea433583dc239077a3a799c8627"
            },
            {
              "fixed": "d5051e604c962ef3d4e5e8e434d0ff4907d2140d"
            },
            {
              "fixed": "dde76d7432c469887d9a95c208083c5f0f73c70d"
            }
          ],
          "repo": "https://github.com/graylog2/graylog2-server",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-gqr6-r77p-c2pj"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-138"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55841.json"
  },
  "details": "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.",
  "id": "CVE-2026-55841",
  "modified": "2026-09-02T03:30:49.780239488Z",
  "published": "2026-08-28T22:11:08.747Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55841.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/Graylog2/graylog2-server/security/advisories/GHSA-gqr6-r77p-c2pj"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55841"
    },
    {
      "type": "FIX",
      "url": "https://github.com/Graylog2/graylog2-server/commit/793df6e8202ea55c15a762e47a2a8a775961dd3f"
    },
    {
      "type": "FIX",
      "url": "https://github.com/Graylog2/graylog2-server/commit/85dc699d6319aea433583dc239077a3a799c8627"
    },
    {
      "type": "FIX",
      "url": "https://github.com/Graylog2/graylog2-server/commit/d5051e604c962ef3d4e5e8e434d0ff4907d2140d"
    },
    {
      "type": "FIX",
      "url": "https://github.com/Graylog2/graylog2-server/commit/dde76d7432c469887d9a95c208083c5f0f73c70d"
    },
    {
      "type": "FIX",
      "url": "https://github.com/Graylog2/graylog2-server/pull/26050"
    },
    {
      "type": "FIX",
      "url": "https://github.com/Graylog2/graylog2-server/pull/26056"
    },
    {
      "type": "FIX",
      "url": "https://github.com/Graylog2/graylog2-server/pull/26057"
    },
    {
      "type": "FIX",
      "url": "https://github.com/Graylog2/graylog2-server/pull/26059"
    }
  ],
  "schema_version": "1.9.0",
  "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": "Graylog: Fortigate syslog message parser can be exploited to modify or delete fields from the original message"
}