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Fencer Vulns
medium 5.9

CVE-2026-47221 json

Envoy: Null pointer deref in internal redirects

published 2026-06-26 4 mo ago modified 2026-10-25 14 d ago also BIT-envoy-2026-47221 , EUVD-2026-39823 , GHSA-rcff-gw58-pjpr

cvss
5.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

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.

Patch / fix

  • bitnami envoy 1.35.13, 1.36.9, 1.37.5, 1.38.3
  • envoyproxy envoy 1.35.13, 1.36.9, 1.37.5, 1.38.3
  • istioctl openSUSE Tumbleweed 1.30.2-1.1

opensuse advisories openSUSE-SU-2026:11141-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-47221 updated cvss 5.9

envoy: Envoy: Null pointer deref in internal redirects

  • Red Hat OpenShift Service Mesh 2 openshift-service-mesh/proxyv2-rhel9
    affected: workaround, no fix planned “Will not fix”
  • Red Hat OpenShift Service Mesh 3.0 openshift-service-mesh/istio-proxyv2-rhel9 1784908682
    fixed: vendor fix RHSA-2026:49705
  • Red Hat OpenShift Service Mesh 3.1 openshift-service-mesh/istio-proxyv2-rhel9 1784953556
    fixed: vendor fix RHSA-2026:49729
  • Red Hat OpenShift Service Mesh 3.2 openshift-service-mesh/istio-proxyv2-rhel9 1784953743
    fixed: vendor fix RHSA-2026:49744
  • Red Hat OpenShift Service Mesh 3.3 openshift-service-mesh/istio-proxyv2-rhel9 1784908639
    fixed: vendor fix RHSA-2026:49765
  • Red Hat OpenShift Service Mesh 3.0 openshift-service-mesh/istio-cni-rhel9 1784885742, openshift-service-mesh/istio-pilot-rhel9 1784885559, openshift-service-mesh/istio-rhel9-operator 1784917979, openshift-service-mesh/istio-must-gather-rhel9 1784796256, openshift-service-mesh/istio-sail-operator-bundle 1784921382, openshift-service-mesh-dev-preview-beta/istio-ztunnel-rhel9 1784886243 Red Hat OpenShift Service Mesh 3.1 openshift-service-mesh/istio-cni-rhel9 1784885281, openshift-service-mesh/istio-pilot-rhel9 1784885133, openshift-service-mesh/istio-rhel9-operator 1784918113, openshift-service-mesh/istio-must-gather-rhel9 1784797072, openshift-service-mesh/istio-sail-operator-bundle 1785036397, openshift-service-mesh-tech-preview/istio-ztunnel-rhel9 1784870048 Red Hat OpenShift Service Mesh 3.2 openshift-service-mesh/istio-cni-rhel9 1784921753, openshift-service-mesh/istio-pilot-rhel9 1784921772, openshift-service-mesh/istio-ztunnel-rhel9 1784922382, openshift-service-mesh/istio-rhel9-operator 1784918117, openshift-service-mesh/istio-must-gather-rhel9 1784839815, openshift-service-mesh/istio-sail-operator-bundle 1785036373 Red Hat OpenShift Service Mesh 3.3 openshift-service-mesh/istio-cni-rhel9 1784885810, openshift-service-mesh/istio-pilot-rhel9 1784885681, openshift-service-mesh/istio-ztunnel-rhel9 1784886337, openshift-service-mesh/istio-rhel9-operator 1785316150, openshift-service-mesh/istio-must-gather-rhel9 1784885505, openshift-service-mesh/istio-sail-operator-bundle 1785322241
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.45% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/envoyproxy/envoy/security/advisories/GHSA-rcff-gw58-pjpr referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
bitnami envoy
>=1.18.0, <1.35.13
>=1.36.0, <1.36.9
>=1.37.0, <1.37.5
>=1.38.0, <1.38.3
1.35.13
1.36.9
1.37.5
1.38.3

Affected products

  • envoyproxy envoy

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.