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Fencer Vulns
medium 5.4

CVE-2023-27488 json

Envoy gRPC client produces invalid protobuf when an HTTP header with non-UTF8 value is received.

published 2023-04-04 3 y ago modified 2026-09-08 2 mo ago also BIT-envoy-2023-27488 , EUVD-2023-31255 , GHSA-9g5w-hqr3-w2ph

cvss
5.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 54%
public exploits
0
none known

Summary

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9, escalation of privileges is possible when `failure_mode_allow: true` is configured for `ext_authz` filter. For affected components that are used for logging and/or visibility, requests may not be logged by the receiving service.

When Envoy was configured to use ext_authz, ext_proc, tap, ratelimit filters, and grpc access log service and an http header with non-UTF-8 data was received, Envoy would generate an invalid protobuf message and send it to the configured service. The receiving service would typically generate an error when decoding the protobuf message. For ext_authz that was configured with ``failure_mode_allow: true``, the request would have been allowed in this case. For the other services, this could have resulted in other unforeseen errors such as a lack of visibility into requests.

As of versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9, Envoy by default sanitizes the values sent in gRPC service calls to be valid UTF-8, replacing data that is not valid UTF-8 with a `!` character. This behavioral change can be temporarily reverted by setting runtime guard `envoy.reloadable_features.service_sanitize_non_utf8_strings` to false. As a workaround, one may set `failure_mode_allow: false` for `ext_authz`.

Patch / fix

  • bitnami envoy 1.22.9, 1.23.6, 1.24.4, 1.25.3
  • envoyproxy envoy 1.22.9, 1.23.6, 1.24.4, 1.25.3

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-2023-27488 updated cvss 8.6

envoy: gRPC client produces invalid protobuf when an HTTP header with non-UTF8 value is received

  • Red Hat OpenShift Service Mesh 2.1 servicemesh-proxy, servicemesh-proxy-wasm
    affected: no fix planned “Will not fix”
  • Red Hat RHOSSM 2.2 for RHEL 8 openshift-service-mesh/proxyv2-rhel8 2.2.9-2
    fixed: vendor fix RHSA-2023:4623
  • Red Hat RHOSSM 2.2 for RHEL 8 openshift-service-mesh/pilot-rhel8 2.2.9-1, openshift-service-mesh/grafana-rhel8 2.2.9-1, openshift-service-mesh/istio-cni-rhel8 2.2.9-1, openshift-service-mesh/ratelimit-rhel8 2.2.9-1, openshift-service-mesh/prometheus-rhel8 2.2.9-1, openshift-service-mesh/istio-must-gather-rhel8 2.2.9-2
    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
none
Automatable
no
Technical impact
partial
Assessed
20 mo ago

Exploit prediction

0.73% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/envoyproxy/envoy/security/advisories/GHSA-9g5w-hqr3-w2ph referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
OSV 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
bitnami envoy
<1.22.9
>=1.23.0, <1.23.6
>=1.24.0, <1.24.4
>=1.25.0, <1.25.3
1.22.9
1.23.6
1.24.4
1.25.3

Affected products

  • envoyproxy envoy

Classification

Weakness
  • CWE-20 Improper Input Validation

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.