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TI-2026-34807 Aliases CVE-2026-47221

Envoy: Null pointer deref in internal redirects

Priority HIGH 66CWE-476Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 4 fixed, 1 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-476.

Summary

Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.18.0 until 1.35.13, 1.36.9, 1.37.5, and 1.38.3, the router filter contains a null pointer dereference vulnerability when handling HTTP 303 (See Other) internal redirects for body-less non-GET/HEAD requests. When a POST, PUT, DELETE, or PATCH request without a body is sent to a route configured with internal redirect policy that includes 303 in redirect_response_codes, and the upstream responds with HTTP 303, the redirect handling code attempts to drain a request body buffer that was never allocated. This results in a segmentation fault that crashes the entire Envoy process. When route configured with internal_redirect_policy including 303 in redirect_response_codes and upstream must return HTTP 303 response, an unauthenticated attacker can exploit this to cause complete denial of service, terminating all active connections. This vulnerability is fixed in 1.35.13, 1.36.9, 1.37.5, and 1.38.3.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00445 38th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial envoy (envoyproxy): 1.38.3, 1.37.5, 1.36.9 +1Red Hat: 4 advisoriesRed Hat: 4 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 1.38.3; 1.37.0 to before 1.37.5; 1.36.0 to before 1.36.9; 1.18.0 to before 1.35.131.38.3, 1.37.5, 1.36.9, 1.35.13Patch availableCNA
  • envoy Vendorenvoyproxy Affected 1.38.0 to before 1.38.3; 1.37.0 to before 1.37.5; 1.36.0 to before 1.36.9; 1.18.0 to before 1.35.13 Fixed in 1.38.3, 1.37.5, 1.36.9, 1.35.13 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*1.18.0 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 1.18.0 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 1.38.3, 1.37.5, 1.36.9, 1.35.13

Red Hat 4 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
  • RHSA-2026:49729 Released 2026-08-03 · Red Hat rating Important
    Red Hat OpenShift Service Mesh 3.1.11
    • Red Hat OpenShift Service Mesh 3.1 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
Show 1 more Red Hat advisories
  • RHSA-2026:49705 Released 2026-08-03 · Red Hat rating Important
    Red Hat OpenShift Service Mesh 3.0.14
    • Red Hat OpenShift Service Mesh 3.0 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: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
OpenShift Service Mesh 2AffectedNo fix planned: Will not fix
Red Hat OpenShift Service Mesh 3.0Fixed RHSA-2026:49705
Red Hat OpenShift Service Mesh 3.1Fixed RHSA-2026:49729
Red Hat OpenShift Service Mesh 3.2Fixed RHSA-2026:49744
Red Hat OpenShift Service Mesh 3.3Fixed RHSA-2026:49765
Not affected: 4 products
  • Red Hat OpenShift Service Mesh 3.0
  • Red Hat OpenShift Service Mesh 3.1
  • Red Hat OpenShift Service Mesh 3.2
  • Red Hat OpenShift Service Mesh 3.3

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-47221

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