2021-32777 | Envoy ext-authz Extension authorization

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
5.1	$0-$5k	0.22

A vulnerability, which was classified as critical, was found in Envoy up to 1.16.4/1.17.3/1.18.3/1.19.0. This affects an unknown part of the component ext-authz Extension. The manipulation with an unknown input leads to a privilege escalation vulnerability. CWE is classifying the issue as CWE-863. This is going to have an impact on confidentiality. The summary by CVE is:

Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affected versions when ext-authz extension is sending request headers to the external authorization service it must merge multiple value headers according to the HTTP spec. However, only the last header value is sent. This may allow specifically crafted requests to bypass authorization. Attackers may be able to escalate privileges when using ext-authz extension or back end service that uses multiple value headers for authorization. A specifically constructed request may be delivered by an untrusted downstream peer in the presence of ext-authz extension. Envoy versions 1.19.1, 1.18.4, 1.17.4, 1.16.5 contain fixes to the ext-authz extension to correctly merge multiple request header values, when sending request for authorization.

The weakness was presented 08/25/2021. It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2021-32777 since 05/12/2021. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 1.16.5, 1.17.4, 1.18.4 or 1.19.1 eliminates this vulnerability. The upgrade is hosted for download at envoyproxy.io.

Name

VulDB Meta Base Score: 5.3
VulDB Meta Temp Score: 5.1

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍
Class: Privilege escalation
CWE: CWE-863
ATT&CK: Unknown

Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfoedit

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Envoy 1.16.5/1.17.4/1.18.4/1.19.1

05/12/2021 CVE assigned
08/25/2021 +105 days Advisory disclosed
08/25/2021 +0 days VulDB entry created
08/29/2021 +4 days VulDB last updateAdvisory: github.com
Status: Confirmed
Confirmation: 🔒

CVE: CVE-2021-32777 (🔒)

Created: 08/25/2021 11:22
Updated: 08/29/2021 08:08
Changes: (1) source_cve_cna
Complete: 🔍

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