High
Traefik: tcp router clears read deadlines before tls forwarding, enabling stalled handshakes (slowloris doS)
Type: advisorySources: OSV
Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.38 and 3.6.9, there is a potential vulnerability in Traefik managing TLS handshake on TCP routers. When Traefik processes a TLS connection on a TCP router, the read deadline used to bound protocol sniffing is cleared before the TLS handshake is completed. When a TLS handshake read error occurs, the code attempts a second handshake with different connection parameters, silently ignoring the initial error. A remote unauthenticated client can exploit this by sending an incomplete TLS record and stopping further data transmission, causing the TLS handshake to stall indefinitely and holding connections open. By opening many such stalled connections in parallel, an attacker can exhaust file descriptors and goroutines, degrading availability of all services on the affected entrypoint. This issue has been patched in versions 2.11.38 and 3.6.9.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-26999
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 18:30 UTC · Revision 1
Source evidence
Traefik: tcp router clears read deadlines before tls forwarding, enabling stalled handshakes (slowloris doS)
core-osv · Original sourcePublished 5 Mar 2026, 16:15 UTC
Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.38 and 3.6.9, there is a potential vulnerability in Traefik managing TLS handshake on TCP routers. When Traefik processes a TLS connection on a TCP router, the read deadline used to bound protocol sniffing is cleared before the TLS handshake is completed. When a TLS handshake read error occurs, the code attempts a second handshake with different connection parameters, silently ignoring the initial error. A remote unauthenticated client can exploit this by sending an incomplete TLS record and stopping further data transmission, causing the TLS handshake to stall indefinitely and holding connections open. By opening many such stalled connections in parallel, an attacker can exhaust file descriptors and goroutines, degrading availability of all services on the affected entrypoint. This issue has been patched in versions 2.11.38 and 3.6.9.
osv:CVE-2026-26999
Complete source record
{
"id": "4962237eeaeae4a4cc4a55cae5754dcee41116c703b3454a99b7ce42f0e3ee75",
"url": "https://osv.dev/vulnerability/CVE-2026-26999",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Traefik: tcp router clears read deadlines before tls forwarding, enabling stalled handshakes (slowloris doS)",
"summary": "Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.38 and 3.6.9, there is a potential vulnerability in Traefik managing TLS handshake on TCP routers. When Traefik processes a TLS connection on a TCP router, the read deadline used to bound protocol sniffing is cleared before the TLS handshake is completed. When a TLS handshake read error occurs, the code attempts a second handshake with different connection parameters, silently ignoring the initial error. A remote unauthenticated client can exploit this by sending an incomplete TLS record and stopping further data transmission, causing the TLS handshake to stall indefinitely and holding connections open. By opening many such stalled connections in parallel, an attacker can exhaust file descriptors and goroutines, degrading availability of all services on the affected entrypoint. This issue has been patched in versions 2.11.38 and 3.6.9.",
"evidence": "osv:CVE-2026-26999",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2026-26999",
"aliases": [
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"GHSA-xw98-5q62-jx94",
"GO-2026-4594"
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],
"modified": "2026-10-28T02:30:31.400627845Z",
"provider": "osv",
"references": [
"https://github.com/traefik/traefik/releases/tag/v2.11.38",
"https://github.com/traefik/traefik/releases/tag/v3.6.9",
"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-26999.json",
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"https://bugzilla.redhat.com/show_bug.cgi?id=2444874"
],
"provider_metadata": {
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"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/26xxx/CVE-2026-26999.json"
}
},
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"evidence": "/id"
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],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 498471,
"published_at": "2026-03-05T16:15:36.437+00:00"
}