CVE-2026-48491 (GCVE-0-2026-48491)
Vulnerability from cvelistv5 – Published: 2026-06-23 19:12 – Updated: 2026-06-23 19:12
VLAI
Title
Traefik: SNICheck ignores wildcard TLSOptions mappings, allowing domain-fronted mTLS bypass
Summary
Traefik is an HTTP reverse proxy and load balancer. From 3.7.0 until 3.7.3, there is a high severity vulnerability in Traefik's domain-fronting protection (SNICheck) that allows an unauthenticated client to bypass mutual TLS enforced through wildcard router TLSOptions. When a router uses a wildcard host rule such as Host(*.example.com) with stricter TLS options (for example RequireAndVerifyClientCert), SNICheck resolves the TLS options for the HTTP Host header using exact map lookups only and never applies wildcard matching. If another permissive SNI is served on the same entrypoint, an attacker can complete the TLS handshake under the permissive options and then send an HTTP Host header targeting the wildcard-protected backend, reaching it without presenting a client certificate. This affects the regular HTTPS / HTTP-2 path and does not require HTTP/3. This vulnerability is fixed in 3.7.3.
Severity
CWE
- CWE-288 - Authentication Bypass Using an Alternate Path or Channel
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/traefik/traefik/security/advis… | x_refsource_CONFIRM |
| https://github.com/traefik/traefik/releases/tag/v3.7.3 | x_refsource_MISC |
{
"containers": {
"cna": {
"affected": [
{
"product": "traefik",
"vendor": "traefik",
"versions": [
{
"status": "affected",
"version": "\u003e= 3.7.0, \u003c 3.7.3"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "Traefik is an HTTP reverse proxy and load balancer. From 3.7.0 until 3.7.3, there is a high severity vulnerability in Traefik\u0027s domain-fronting protection (SNICheck) that allows an unauthenticated client to bypass mutual TLS enforced through wildcard router TLSOptions. When a router uses a wildcard host rule such as Host(*.example.com) with stricter TLS options (for example RequireAndVerifyClientCert), SNICheck resolves the TLS options for the HTTP Host header using exact map lookups only and never applies wildcard matching. If another permissive SNI is served on the same entrypoint, an attacker can complete the TLS handshake under the permissive options and then send an HTTP Host header targeting the wildcard-protected backend, reaching it without presenting a client certificate. This affects the regular HTTPS / HTTP-2 path and does not require HTTP/3. This vulnerability is fixed in 3.7.3."
}
],
"metrics": [
{
"cvssV4_0": {
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "NETWORK",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"privilegesRequired": "NONE",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "HIGH",
"subIntegrityImpact": "HIGH",
"userInteraction": "NONE",
"vectorString": "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",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-288",
"description": "CWE-288: Authentication Bypass Using an Alternate Path or Channel",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-06-23T19:12:10.819Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/traefik/traefik/security/advisories/GHSA-5r4w-85f3-pw66",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/traefik/traefik/security/advisories/GHSA-5r4w-85f3-pw66"
},
{
"name": "https://github.com/traefik/traefik/releases/tag/v3.7.3",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/traefik/traefik/releases/tag/v3.7.3"
}
],
"source": {
"advisory": "GHSA-5r4w-85f3-pw66",
"discovery": "UNKNOWN"
},
"title": "Traefik: SNICheck ignores wildcard TLSOptions mappings, allowing domain-fronted mTLS bypass"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-48491",
"datePublished": "2026-06-23T19:12:10.819Z",
"dateReserved": "2026-05-21T15:33:08.291Z",
"dateUpdated": "2026-06-23T19:12:10.819Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-48491",
"date": "2026-06-24",
"epss": "0.00228",
"percentile": "0.13294"
}
}
}
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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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