CVE-2023-27488
Envoy gRPC client produces invalid protobuf when an HTTP header with non-UTF8 value is received.
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
5.4
Envoy gRPC client produces invalid protobuf when an HTTP header with non-UTF8 value is received.
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.
- Record
CVE-2023-27488- CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N - Weakness
- CWE-20
- Updated
- 2026-11-02
EUVDEUVD-2023-31255
5.4
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.
- Record
EUVD-2023-31255- CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N - Updated
- 2026-11-03
NVD
5.4
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.
- Record
CVE-2023-27488- CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N - CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-20
- Updated
- 2026-11-02
OSV
5.4
Envoy gRPC client produces invalid protobuf when an HTTP header with non-UTF8 value is received.
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.
- Record
CVE-2023-27488- CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N - Weakness
- CWE-20
- Updated
- 2026-11-02
OSVBIT-envoy-2023-27488 No score
Envoy gRPC client produces invalid protobuf when an HTTP header with non-UTF8 value is received.
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.
- Record
BIT-envoy-2023-27488- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
envoyBitnami |
before 1.22.9, 1.23.0 up to 1.23.6, 1.24.0 up to 1.24.4, 1.25.0 up to 1.25.3 | 1.22.91.23.61.24.41.25.3 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, published | EUVD | |
| first indexed | CVE List, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2023-27488 is a medium vulnerability (CVSS 5.4) in Envoyproxy Envoy, published April 4, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.73%, the 54th percentile. Fixed in envoy 1.22.9.