High
Traefik: headerField underscore-variant identity spoofing in BasicAuth / DigestAuth / ForwardAuth
Type: advisorySources: OSV
Traefik is an HTTP reverse proxy and load balancer. Prior to v2.11.51, v3.6.22, and v3.7.6, Traefik's BasicAuth, DigestAuth, and ForwardAuth middlewares strip canonical-cased spoofed identity headers before writing Traefik's own value, but do not account for underscore-variant header names, which many backends normalize identically to dashed forms. An attacker able to reach a protected route can inject an underscore-variant header that survives Traefik's stripping and reaches the backend alongside, or on the unauthenticated ForwardAuth authResponseHeaders path instead of, the value Traefik intended to set, spoofing identity or authorization context. This issue is fixed in versions v2.11.51, v3.6.22, and v3.7.6.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-54763
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 03:55 UTC · Revision 1
Source evidence
Traefik: headerField underscore-variant identity spoofing in BasicAuth / DigestAuth / ForwardAuth
core-osv · Original sourcePublished 6 Jul 2026, 20:33 UTC
Traefik is an HTTP reverse proxy and load balancer. Prior to v2.11.51, v3.6.22, and v3.7.6, Traefik's BasicAuth, DigestAuth, and ForwardAuth middlewares strip canonical-cased spoofed identity headers before writing Traefik's own value, but do not account for underscore-variant header names, which many backends normalize identically to dashed forms. An attacker able to reach a protected route can inject an underscore-variant header that survives Traefik's stripping and reaches the backend alongside, or on the unauthenticated ForwardAuth authResponseHeaders path instead of, the value Traefik intended to set, spoofing identity or authorization context. This issue is fixed in versions v2.11.51, v3.6.22, and v3.7.6.
osv:CVE-2026-54763
Complete source record
{
"id": "c293127abfaf933a602841bf9ca5dba770d1dcd47218f5d5078aa471898df00f",
"url": "https://osv.dev/vulnerability/CVE-2026-54763",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Traefik: headerField underscore-variant identity spoofing in BasicAuth / DigestAuth / ForwardAuth",
"summary": "Traefik is an HTTP reverse proxy and load balancer. Prior to v2.11.51, v3.6.22, and v3.7.6, Traefik's BasicAuth, DigestAuth, and ForwardAuth middlewares strip canonical-cased spoofed identity headers before writing Traefik's own value, but do not account for underscore-variant header names, which many backends normalize identically to dashed forms. An attacker able to reach a protected route can inject an underscore-variant header that survives Traefik's stripping and reaches the backend alongside, or on the unauthenticated ForwardAuth authResponseHeaders path instead of, the value Traefik intended to set, spoofing identity or authorization context. This issue is fixed in versions v2.11.51, v3.6.22, and v3.7.6.",
"evidence": "osv:CVE-2026-54763",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2026-54763",
"aliases": [
"CVE-2026-54763",
"GHSA-x677-9fxg-v5c5",
"GO-2026-6211"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/traefik/traefik",
"type": "GIT",
"events": [
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"introduced": "0"
},
{
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},
{
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},
{
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},
{
"introduced": "04aa6bb4f9776f2ba87e5cd181d250e3610e6419"
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{
"fixed": "1afefcd7149ff331fa73ef62fb3dd69e3ced37ba"
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{
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"range": [
{
"introduced": "0"
},
{
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"source": "CPE_RANGE"
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{
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"range": [
{
"introduced": "3.0.0"
},
{
"fixed": "3.6.22"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "3.7.0"
},
{
"fixed": "3.7.6"
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],
"source": "CPE_RANGE"
},
{
"range": [
{
"fixed": "108a5264473a2cbc8f12d6d691a3c6553cdf2c1b"
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"source": "REFERENCES_COMMIT"
}
]
}
}
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"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-54763.json"
}
}
],
"modified": "2026-10-28T02:30:25.653268452Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54763.json",
"https://github.com/traefik/traefik/security/advisories/GHSA-x677-9fxg-v5c5",
"https://nvd.nist.gov/vuln/detail/CVE-2026-54763",
"https://github.com/traefik/traefik/commit/108a5264473a2cbc8f12d6d691a3c6553cdf2c1b",
"https://github.com/traefik/traefik/pull/13262"
],
"provider_metadata": {
"cwe_ids": [
"CWE-178",
"CWE-290",
"CWE-345"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54763.json"
}
},
"related_cves": [
{
"value": "CVE-2026-54763",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 492294,
"published_at": "2026-07-06T20:33:36.059+00:00"
}