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TI-2026-36014 Aliases CVE-2026-48743

Envoy: HTTP/3 to HTTP/1 request smuggling via headers-only request with nonzero Content-Length

Priority HIGH 66CWE-444Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
Low · High · None
Fix status
Partial Red Hat: 2 fixed, 1 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.

Summary

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1, Envoy can translate a downstream HTTP/3 request that is complete at the transport layer (HEADERS with FIN / headers-only close) but still carries a nonzero Content-Length into a complete upstream HTTP/1 request with unresolved body debt. In an HTTP/1 upstream deployment where the origin replies before reading the declared body and keeps the connection reusable, the beginning of the next Envoy-generated upstream request can be consumed as the first request's body. The remaining bytes are then parsed by the origin as a new HTTP/1 request. This was reproduced as a route-bypass/desync: direct /pwn was denied by Envoy, but the second downstream H3 stream received the response for backend-parsed GET /pwn HTTP/1.1. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00298 22nd percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial envoy (envoyproxy): 1.38.1, 1.37.3, 1.36.7 +1Red Hat: 2 advisoriesRed Hat: 2 fixed, 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
envoyproxyenvoy1.38.0 to before 1.38.1; 1.37.0 to before 1.37.3; 1.36.0 to before 1.36.7; 1.35.0 to before 1.35.111.38.1, 1.37.3, 1.36.7, 1.35.11Patch availableCNA
  • envoy Vendorenvoyproxy Affected 1.38.0 to before 1.38.1; 1.37.0 to before 1.37.3; 1.36.0 to before 1.36.7; 1.35.0 to before 1.35.11 Fixed in 1.38.1, 1.37.3, 1.36.7, 1.35.11 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*1.35.0 to before 1.35.13; 1.36.0 to before 1.36.9; 1.37.0 to before 1.37.5; 1.38.0 to before 1.38.3Vulnerableenvoyproxy
  • cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* Versions 1.35.0 to before 1.35.13; 1.36.0 to before 1.36.9; 1.37.0 to before 1.37.5; 1.38.0 to before 1.38.3 Vulnerable ·envoyproxy

Remediation

  • Fix · CNA envoy (envoyproxy) Fixed in 1.38.1, 1.37.3, 1.36.7, 1.35.11

Red Hat 2 advisories

  • RHSA-2026:49765 Released 2026-08-03 · Red Hat rating Important
    Red Hat OpenShift Service Mesh 3.3.6
    • Red Hat OpenShift Service Mesh 3.3 registry.redhat.io/openshift-service-mesh/istio-cni-rhel9, registry.redhat.io/openshift-service-mesh/istio-pilot-rhel9, registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9 +1
  • RHSA-2026:49744 Released 2026-08-03 · Red Hat rating Important
    Red Hat OpenShift Service Mesh 3.2.8
    • Red Hat OpenShift Service Mesh 3.2 registry.redhat.io/openshift-service-mesh/istio-cni-rhel9, registry.redhat.io/openshift-service-mesh/istio-pilot-rhel9, registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9 +1

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
OpenShift Service Mesh 2AffectedNo fix planned: Will not fix
Red Hat OpenShift Service Mesh 3.2Fixed RHSA-2026:49744
Red Hat OpenShift Service Mesh 3.3Fixed RHSA-2026:49765
Not affected: 2 products
  • Red Hat OpenShift Service Mesh 3.2
  • Red Hat OpenShift Service Mesh 3.3

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-48743

References

Exploit 1

  • TI-2026-79288 Out-of-bounds write in Google Brotli decoder KEVCVSS 4.0CRITICAL 9.2
  • TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
  • TI-2024-20001 HTTP/2: CPU exhaustion due to CONTINUATION frame flood CVSS 3.1HIGH 7.5
  • TI-2024-18524 HTTP/2: memory exhaustion due to CONTINUATION frame flood CVSS 3.1HIGH 7.5
  • TI-2023-12215 Envoy client may fake the header `x-envoy-original-path` CVSS 3.1CRITICAL 9.1
  • TI-2023-18002 Envoy vulnerable to OAuth2 credentials exploit with permanent validity CVSS 3.1CRITICAL 9.8
See all 126 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences