High
Traefik: Cross-user response poisoning via proxied CONNECT on Traefik's shared backend keep-alive pool
Type: advisorySources: OSV
Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.53, 3.6.24, and 3.7.9, Traefik's default HTTP reverse proxy forwards a plain HTTP/2 or HTTP/3 CONNECT request and its body to an HTTP/1.1 upstream through a shared net/http.Transport. When the upstream answers the CONNECT with a keep-alive non-2xx response and does not drain the body, Traefik returns the desynchronized backend socket to its shared pool and reuses it for other clients. An unauthenticated attacker can use this behavior to make a different client read the attacker's smuggled response, which can include authenticated or private content from another request. The ForwardAuth middleware with forwardBody true and preserveRequestMethod true can re-issue a CONNECT with the buffered body attached, exposing the auth-client pool to the same desynchronization. This issue is fixed in 2.11.53, 3.6.24, and 3.7.9.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-71324
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 2 Nov 2026, 19:58 UTC · Revision 1
Source evidence
Traefik: Cross-user response poisoning via proxied CONNECT on Traefik's shared backend keep-alive pool
core-osv · Original sourcePublished 6 Aug 2026, 15:56 UTC
Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.53, 3.6.24, and 3.7.9, Traefik's default HTTP reverse proxy forwards a plain HTTP/2 or HTTP/3 CONNECT request and its body to an HTTP/1.1 upstream through a shared net/http.Transport. When the upstream answers the CONNECT with a keep-alive non-2xx response and does not drain the body, Traefik returns the desynchronized backend socket to its shared pool and reuses it for other clients. An unauthenticated attacker can use this behavior to make a different client read the attacker's smuggled response, which can include authenticated or private content from another request. The ForwardAuth middleware with forwardBody true and preserveRequestMethod true can re-issue a CONNECT with the buffered body attached, exposing the auth-client pool to the same desynchronization. This issue is fixed in 2.11.53, 3.6.24, and 3.7.9.
osv:CVE-2026-71324
Complete source record
{
"id": "21839073c04584873dc354528694268d57400a61bfd71ed662d127cba6fe0837",
"url": "https://osv.dev/vulnerability/CVE-2026-71324",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Traefik: Cross-user response poisoning via proxied CONNECT on Traefik's shared backend keep-alive pool",
"summary": "Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.53, 3.6.24, and 3.7.9, Traefik's default HTTP reverse proxy forwards a plain HTTP/2 or HTTP/3 CONNECT request and its body to an HTTP/1.1 upstream through a shared net/http.Transport. When the upstream answers the CONNECT with a keep-alive non-2xx response and does not drain the body, Traefik returns the desynchronized backend socket to its shared pool and reuses it for other clients. An unauthenticated attacker can use this behavior to make a different client read the attacker's smuggled response, which can include authenticated or private content from another request. The ForwardAuth middleware with forwardBody true and preserveRequestMethod true can re-issue a CONNECT with the buffered body attached, exposing the auth-client pool to the same desynchronization. This issue is fixed in 2.11.53, 3.6.24, and 3.7.9.",
"evidence": "osv:CVE-2026-71324",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2026-71324",
"aliases": [
"CVE-2026-71324",
"GHSA-3ccp-42pg-hgv6",
"GO-2026-6201"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N"
}
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"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-71324.json"
}
}
],
"modified": "2026-10-28T02:30:23.188206035Z",
"provider": "osv",
"references": [
"https://github.com/traefik/traefik/releases/tag/v2.11.53",
"https://github.com/traefik/traefik/releases/tag/v3.6.24",
"https://github.com/traefik/traefik/releases/tag/v3.7.9",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/71xxx/CVE-2026-71324.json",
"https://github.com/traefik/traefik/security/advisories/GHSA-3ccp-42pg-hgv6",
"https://nvd.nist.gov/vuln/detail/CVE-2026-71324",
"https://github.com/traefik/traefik/commit/04d36f28e4eae7535e96a6351dd9f7bfb48a30e7",
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"https://github.com/traefik/traefik/pull/13542",
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"https://github.com/traefik/traefik/pull/13556"
],
"provider_metadata": {
"cwe_ids": [
"CWE-444"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/71xxx/CVE-2026-71324.json"
}
},
"related_cves": [
{
"value": "CVE-2026-71324",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 489497,
"published_at": "2026-08-06T15:56:33.112+00:00"
}