CVE-2021-21378 (High) detected in envoy-wasmae02dc6bdd5c5ea61c3869395d81689e34988156

[mend-bolt-for-github]

CVE-2021-21378 - High Severity Vulnerability

Vulnerable Library - envoy-wasmae02dc6bdd5c5ea61c3869395d81689e34988156

*ATTENTION!: The content of this repo is merged into https://github.com/envoyproxy/envoy and future development is happening there.

Library home page: https://github.com/envoyproxy/envoy-wasm.git

Found in HEAD commit: 320650059a0b0796f39380aaca16815f2f8a4625

Found in base branch: master

Vulnerable Source Files (1)

envoy/source/extensions/filters/http/jwt_authn/verifier.cc

Vulnerability Details

Envoy is a cloud-native high-performance edge/middle/service proxy. In Envoy version 1.17.0 an attacker can bypass authentication by presenting a JWT token with an issuer that is not in the provider list when Envoy's JWT Authentication filter is configured with the allow_missing requirement under requires_any due to a mistake in implementation. Envoy's JWT Authentication filter can be configured with the allow_missing requirement that will be satisfied if JWT is missing (JwtMissed error) and fail if JWT is presented or invalid. Due to a mistake in implementation, a JwtUnknownIssuer error was mistakenly converted to JwtMissed when requires_any was configured. So if allow_missing was configured under requires_any, an attacker can bypass authentication by presenting a JWT token with an issuer that is not in the provider list. Integrity may be impacted depending on configuration if the JWT token is used to protect against writes or modifications. This regression was introduced on 2020/11/12 in PR 13839 which fixed handling allow_missing under RequiresAny in a JwtRequirement (see issue 13458). The AnyVerifier aggregates the children verifiers' results into a final status where JwtMissing is the default error. However, a JwtUnknownIssuer was mistakenly treated the same as a JwtMissing error and the resulting final aggregation was the default JwtMissing. As a result, allow_missing would allow a JWT token with an unknown issuer status. This is fixed in version 1.17.1 by PR 15194. The fix works by preferring JwtUnknownIssuer over a JwtMissing error, fixing the accidental conversion and bypass with allow_missing. A user could detect whether a bypass occurred if they have Envoy logs enabled with debug verbosity. Users can enable component level debug logs for JWT. The JWT filter logs will indicate that there is a request with a JWT token and a failure that the JWT token is missing.

Publish Date: 2021-03-11

URL: CVE-2021-21378

CVSS 3 Score Details (8.2)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: High
  • Integrity Impact: Low
  • Availability Impact: None

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: GHSA-4996-m8hf-hj27

Release Date: 2021-03-11

Fix Resolution: v1.17.1

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