Authorization bypass via malformed gRPC protobuf
Published Apr 4, 2023 · Updated Feb 11, 2025
Improper input validation in Envoy allows remote attackers to bypass authorization checks via HTTP headers containing non-UTF-8 data. The gRPC client serializes such header values without UTF-8 sanitization, producing an invalid protobuf that the external authorization service rejects. Exploitation requires the ext_authz filter with failure_mode_allow set to true; the decoding error also leaves affected visibility-service requests unlogged.
Summary
What happened
Improper input validation in Envoy allows remote attackers to bypass authorization checks via HTTP headers containing non-UTF-8 data. The gRPC client serializes such header values without UTF-8 sanitization, producing an invalid protobuf that the external authorization service rejects. Exploitation requires the ext_authz filter with failure_mode_allow set to true; the decoding error also leaves affected visibility-service requests unlogged.
The record
- CVE
- CVE-2023-27488
- Published
- Apr 4, 2023
- Updated
- Feb 11, 2025
- Vendor
- Envoy Proxy
- Product
- Envoy
- Classifications
- CWE-20, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 4, 2023CVE publishedPublication date reported by the CVE source.
- Feb 11, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 1.22.9
- Affected versionversion=>= 1.23.0, < 1.23.6
- Affected versionversion=>= 1.24.0, < 1.24.4
- Affected versionversion=>= 1.25.0, <1.25.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- Upstream non-UTF-8 header reproductionproof of concept · unverified
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Technologies
Your stack
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Your stack
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