CVE-2021-32777 Incorrect concatenation of multiple value request headers in ext-authz extension
Attackers can bypass authorization checks in Envoy's ext-authz extension by crafting requests with multiple header values, potentially escalating privileges.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-32777?
CVE-2021-32777 is a high-severity authentication bypass vulnerability in Envoyproxy Envoy, published on 24 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2021-32777?
1 open source package ship an affected version, including envoy. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
envoy Bitnami | From 1.16.0 | 1.16.5, 1.17.4, 1.18.4, 1.19.1 |
Products include Envoyproxy Envoy.
How do I fix CVE-2021-32777?
Upgrade envoy to a fixed version for your release line: 1.16.5, 1.17.4, 1.18.4 or 1.19.1.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2021-32777 being exploited?
There is no known exploitation of CVE-2021-32777 in the wild and no public exploit code.
Other vulnerabilities in Envoyproxy Envoy
Sources
Also known as BIT-envoy-2021-32777, GHSA-6g4j-5vrw-2m8h.