Auth bypass in Envoyproxy Envoy
CVE-2021-32777
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.
EPSS: 0.033 (87.8th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 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.
Affected products
- Envoyproxy Envoy — versions >= 1.19.0, < 1.19.1, >= 1.16.0, < 1.16.5, >= 1.17.0, < 1.17.4
Weakness classification (CWE)
Public proof-of-concept exploits
References
- security-advisories@github.com (x_refsource_CONFIRM, Third Party Advisory)
- security-advisories@github.com (x_refsource_MISC, Release Notes, Vendor Advisory)
Frequently asked questions
- What is CVE-2021-32777?
- CVE-2021-32777 is a high-severity vulnerability in Envoyproxy Envoy, classified under CWE-551. CVSS score: 8.6/10. Published 2021-08-24.
- How severe is CVE-2021-32777?
- High severity. CVSS v3 base score is 8.6 out of 10.
- Is CVE-2021-32777 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.