CVE-2021-32779 Detail

Current Description

Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affected versions envoy incorrectly handled a URI '#fragment' element as part of the path element. Envoy is configured with an RBAC filter for authorization or similar mechanism with an explicit case of a final "/admin" path element, or is using a negative assertion with final path element of "/admin". The client sends request to "/app1/admin#foo". In Envoy prior to 1.18.0, or 1.18.0+ configured with path_normalization=false. Envoy treats fragment as a suffix of the query string when present, or as a suffix of the path when query string is absent, so it evaluates the final path element as "/admin#foo" and mismatches with the configured "/admin" path element. In Envoy 1.18.0+ configured with path_normalization=true. Envoy transforms this to /app1/admin%23foo and mismatches with the configured /admin prefix. The resulting URI is sent to the next server-agent with the offending "#foo" fragment which violates RFC3986 or with the nonsensical "%23foo" text appended. A specifically constructed request with URI containing '#fragment' element delivered by an untrusted client in the presence of path based request authorization resulting in escalation of Privileges when path based request authorization extensions. Envoy versions 1.19.1, 1.18.4, 1.17.4, 1.16.5 contain fixes that removes fragment from URI path in incoming requests.


View Analysis Description

Severity



CVSS 3.x Severity and Metrics:

NIST CVSS score
NIST: NVD
Base Score:  8.3 HIGH
Vector:  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

Nist CVSS score does not match with CNA score
CNA:  GitHub, Inc.
Base Score:  8.6 HIGH
Vector:  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N


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Note: It is possible that the NVD CVSS may not match that of the CNA. The most common reason for this is that publicly available information does not provide sufficient detail or that information simply was not available at the time the CVSS vector string was assigned.

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Hyperlink Resource
https://github.com/envoyproxy/envoy/security/advisories/GHSA-r222-74fw-jqr9 Third Party Advisory 
https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_history Vendor Advisory 

Weakness Enumeration

CWE-ID CWE Name Source
CWE-863 Incorrect Authorization cwe source acceptance level NIST   Provider acceptance level GitHub, Inc.  
CWE-551 Incorrect Behavior Order: Authorization Before Parsing and Canonicalization Provider acceptance level GitHub, Inc.  

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Change History

2 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2021-32779
NVD Published Date:
08/24/2021
NVD Last Modified:
09/07/2021
Source:
GitHub, Inc.