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High, CVSS 7.0amended

Traefik: Cross-user response poisoning via proxied CONNECT on Traefik's shared backend keep-alive pool

CVE-2026-71324GHSA-3ccp-42pg-hgv6

What to do

Partial vendor fix. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Go github.com/traefik/traefik/v3

    Affected
    <= 3.6.23>= 3.7.0, <= 3.7.8
    Fixed in
    3.7.9, 3.6.24

  • Go github.com/traefik/traefik/v2

    Affected
    <= 2.11.52
    Fixed in
    2.11.53

  • Go github.com/traefik/traefik

    Affected
    <= 1.7.34
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
7.0 · 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 · score source
EPSS
  • CVE-2026-71324: 1.06% estimated exploitation activity in the next 30 days; percentile 64.69 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary There is a critical vulnerability in Traefik's default HTTP reverse proxy that leads to unauthenticated cross-user response poisoning. When a client opens an HTTP/2 or HTTP/3 CONNECT request, Traefik forwards it — body included — to an HTTP/1.1 upstream over a shared net/http.Transport. If the upstream answers the CONNECT with a keep-alive non-2xx response without draining the body, the now-desynchronized backend socket is returned to Traefik's shared connection pool and reused for other clients, letting an attacker make a different client read a response the attacker smuggled — which may be another user's authenticated or private content. The entrypoint's sanitizePath option (default true) is not a reliable defense: backends that answer CONNECT / with a keep-alive non-2xx remain exploitable. The experimental FastProxy implementation was not affected. The issue is fixed by deferring the forwarded CONNECT payload until the backend accepts the tunnel, by not returning CONNECT…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 4 · amended ·

    Amended from ghsa record GHSA-3ccp-42pg-hgv6

  2. Revision 3 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 2 · amended ·

    Amended from osv record GO-2026-6201

  4. Revision 1 · created ·

    Published from osv record GHSA-3ccp-42pg-hgv6

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-71324

Advisory: Traefik: Cross-user response poisoning via proxied CONNECT on Traefik's shared backend keep-alive pool
IDs: CVE-2026-71324, GHSA-3ccp-42pg-hgv6
Record: https://patchnext.com/advisories/cve-2026-71324 (revision 4, source checked 26 Oct 2026, 15:28 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/traefik/traefik/v3 3.7.9, 3.6.24; github.com/traefik/traefik/v2 2.11.53. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/traefik/traefik/v3: affected <= 3.6.23; >= 3.7.0, <= 3.7.8; fixed in 3.7.9, 3.6.24
- Go github.com/traefik/traefik/v2: affected <= 2.11.52; fixed in 2.11.53
- Go github.com/traefik/traefik: affected <= 1.7.34

## Suggested inspection (read-only)
- Go github.com/traefik/traefik/v3: check the installed version with your package manager.
- Go github.com/traefik/traefik/v2: check the installed version with your package manager.
- Go github.com/traefik/traefik: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/traefik/traefik/v3, github.com/traefik/traefik/v2, github.com/traefik/traefik.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-3ccp-42pg-hgv6 (OSV record GHSA-3ccp-42pg-hgv6 lists affected ranges: Go github.com/traefik/traefik/v2 >=0 =0 =3.7.0 =0 <=1.7.34)
- Verified: https://osv.dev/vulnerability/GO-2026-6201 (OSV record GO-2026-6201 lists affected ranges: Go github.com/traefik/traefik >=0; Go github.com/traefik/traefik/v2 >=0 =0 =3.7.0 <3.7.9 (fixed))
- Verified: https://github.com/advisories/GHSA-3ccp-42pg-hgv6 (GitHub-reviewed advisory GHSA-3ccp-42pg-hgv6 lists affected ranges: Go github.com/traefik/traefik/v2 >=0 =0 =3.7.0 =0 <=1.7.34)

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