CVE-2026-55841 (GCVE-0-2026-55841)
Vulnerability from cvelistv5 – Published: 2026-08-28 22:11 – Updated: 2026-08-28 22:11
VLAI
EPSS
VEX
Title
Graylog: Fortigate syslog message parser can be exploited to modify or delete fields from the original message
Summary
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.
Severity
7.5 (High)
CWE
- CWE-138 - Improper Neutralization of Special Elements
Assigner
References
9 references
| URL | Tags |
|---|---|
| https://github.com/Graylog2/graylog2-server/secur… | x_refsource_CONFIRM |
| https://github.com/Graylog2/graylog2-server/pull/26050 | x_refsource_MISC |
| https://github.com/Graylog2/graylog2-server/pull/26056 | x_refsource_MISC |
| https://github.com/Graylog2/graylog2-server/pull/26057 | x_refsource_MISC |
| https://github.com/Graylog2/graylog2-server/pull/26059 | x_refsource_MISC |
| https://github.com/Graylog2/graylog2-server/commi… | x_refsource_MISC |
| https://github.com/Graylog2/graylog2-server/commi… | x_refsource_MISC |
| https://github.com/Graylog2/graylog2-server/commi… | x_refsource_MISC |
| https://github.com/Graylog2/graylog2-server/commi… | x_refsource_MISC |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Graylog2 | graylog2-server |
Affected:
< 6.3.12
Affected: >= 7.0.0-alpha.1, < 7.0.7 Affected: >= 7.1.0-alpha.1, < 7.1.2 |
guessed |
{
"containers": {
"cna": {
"affected": [
{
"product": "graylog2-server",
"vendor": "Graylog2",
"versions": [
{
"status": "affected",
"version": "\u003c 6.3.12"
},
{
"status": "affected",
"version": "\u003e= 7.0.0-alpha.1, \u003c 7.0.7"
},
{
"status": "affected",
"version": "\u003e= 7.1.0-alpha.1, \u003c 7.1.2"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "NONE",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-138",
"description": "CWE-138: Improper Neutralization of Special Elements",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-28T22:11:08.747Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/Graylog2/graylog2-server/security/advisories/GHSA-gqr6-r77p-c2pj",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/Graylog2/graylog2-server/security/advisories/GHSA-gqr6-r77p-c2pj"
},
{
"name": "https://github.com/Graylog2/graylog2-server/pull/26050",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/Graylog2/graylog2-server/pull/26050"
},
{
"name": "https://github.com/Graylog2/graylog2-server/pull/26056",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/Graylog2/graylog2-server/pull/26056"
},
{
"name": "https://github.com/Graylog2/graylog2-server/pull/26057",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/Graylog2/graylog2-server/pull/26057"
},
{
"name": "https://github.com/Graylog2/graylog2-server/pull/26059",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/Graylog2/graylog2-server/pull/26059"
},
{
"name": "https://github.com/Graylog2/graylog2-server/commit/793df6e8202ea55c15a762e47a2a8a775961dd3f",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/Graylog2/graylog2-server/commit/793df6e8202ea55c15a762e47a2a8a775961dd3f"
},
{
"name": "https://github.com/Graylog2/graylog2-server/commit/85dc699d6319aea433583dc239077a3a799c8627",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/Graylog2/graylog2-server/commit/85dc699d6319aea433583dc239077a3a799c8627"
},
{
"name": "https://github.com/Graylog2/graylog2-server/commit/d5051e604c962ef3d4e5e8e434d0ff4907d2140d",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/Graylog2/graylog2-server/commit/d5051e604c962ef3d4e5e8e434d0ff4907d2140d"
},
{
"name": "https://github.com/Graylog2/graylog2-server/commit/dde76d7432c469887d9a95c208083c5f0f73c70d",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/Graylog2/graylog2-server/commit/dde76d7432c469887d9a95c208083c5f0f73c70d"
}
],
"source": {
"advisory": "GHSA-gqr6-r77p-c2pj",
"discovery": "UNKNOWN"
},
"title": "Graylog: Fortigate syslog message parser can be exploited to modify or delete fields from the original message"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-55841",
"datePublished": "2026-08-28T22:11:08.747Z",
"dateReserved": "2026-06-17T16:29:38.865Z",
"dateUpdated": "2026-08-28T22:11:08.747Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-55841",
"date": "2026-08-29",
"epss": "0.00355",
"percentile": "0.28276"
},
"nvd": "{\"cve\":{\"id\":\"CVE-2026-55841\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-08-28T23:17:07.840\",\"lastModified\":\"2026-08-28T23:17:07.840\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"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.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"Graylog2\",\"product\":\"graylog2-server\",\"versions\":[{\"version\":\"\u003c 6.3.12\",\"status\":\"affected\"},{\"version\":\"\u003e= 7.0.0-alpha.1, \u003c 7.0.7\",\"status\":\"affected\"},{\"version\":\"\u003e= 7.1.0-alpha.1, \u003c 7.1.2\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N\",\"baseScore\":7.5,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":3.9,\"impactScore\":3.6}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-138\"}]}],\"references\":[{\"url\":\"https://github.com/Graylog2/graylog2-server/commit/793df6e8202ea55c15a762e47a2a8a775961dd3f\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/Graylog2/graylog2-server/commit/85dc699d6319aea433583dc239077a3a799c8627\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/Graylog2/graylog2-server/commit/d5051e604c962ef3d4e5e8e434d0ff4907d2140d\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/Graylog2/graylog2-server/commit/dde76d7432c469887d9a95c208083c5f0f73c70d\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/Graylog2/graylog2-server/pull/26050\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/Graylog2/graylog2-server/pull/26056\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/Graylog2/graylog2-server/pull/26057\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/Graylog2/graylog2-server/pull/26059\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/Graylog2/graylog2-server/security/advisories/GHSA-gqr6-r77p-c2pj\",\"source\":\"security-advisories@github.com\"}]}}"
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
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.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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