THREATPORT/VULNERABILITY/CVE-2021-32777
HIGH SEVERITY

CVE-2021-32777

Envoy vulnerability

CVSS
8.6
EPSS
3.3%
EPSS pct
87th
Exploited
No known
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.
Affected vendor
Envoyproxy
Affected product
Envoy
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
Weakness type (CWE)
Published
2021-08-24

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, low attack complexity, requiring no privileges, no user interaction. Successful exploitation leads to high impact to confidentiality.

Its EPSS score of 3.3% reflects a lower probability of exploitation activity in the wild over the next 30 days, placing it above 87% of all scored CVEs.

Check your external exposure to CVE-2021-32777

  • Confirm whether Envoyproxy Envoy is running on any internet-facing host or subdomain.
  • Match discovered service fingerprints against the version affected by CVE-2021-32777.
  • Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2021-32777

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