Vulnerability CVE-2021-32779

Vulnerability Name:

CVE-2021-32779 (CCN-208235)

Assigned:

2021-08-24

Published:

2021-08-24

Updated:

2022-10-25

Summary:

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.

CVSS v3 Severity:

8.3 High (CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L)
7.2 High (Temporal CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L/E:U/RL:O/RC:C)

Exploitability Metrics:	Attack Vector (AV): Network Attack Complexity (AC): Low Privileges Required (PR): None User Interaction (UI): None
Scope:	Scope (S): Changed
Impact Metrics:	Confidentiality (C): Low Integrity (I): Low Availibility (A): Low

8.6 High (CCN CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N)
7.5 High (CCN Temporal CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N/E:U/RL:O/RC:C)

Exploitability Metrics:	Attack Vector (AV): Network Attack Complexity (AC): Low Privileges Required (PR): None User Interaction (UI): None
Scope:	Scope (S): Changed
Impact Metrics:	Confidentiality (C): High Integrity (I): None Availibility (A): None

CVSS v2 Severity:

7.5 High (CVSS v2 Vector: AV:N/AC:L/Au:N/C:P/I:P/A:P)

Exploitability Metrics:	Access Vector (AV): Network Access Complexity (AC): Low Authentication (Au): None
Impact Metrics:	Confidentiality (C): Partial Integrity (I): Partial Availibility (A): Partial

7.8 High (CCN CVSS v2 Vector: AV:N/AC:L/Au:N/C:C/I:N/A:N)

Exploitability Metrics:	Access Vector (AV): Network Access Complexity (AC): Low Athentication (Au): None
Impact Metrics:	Confidentiality (C): Complete Integrity (I): None Availibility (A): None