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CVE-2021-32779
CVE ID
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CVE-2021-32779
MITRE ATT&CK
Collection
Command and Control
Credential Access
Defense Evasion
Discovery
Execution
Exfiltration
Impact
Initial Access
Lateral Movement
Persistence
Privilege Escalation
Topic Tags
Description
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.
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CVSS V3 Severity and Metrics
General Information
Vendors
- envoyproxy
Products
- envoy,
- envoy 1.19.0
References
Additional Info
Technical Analysis
Report as Emergent Threat Response
Report as Zero-day Exploit
Report as Exploited in the Wild
CVE ID
AttackerKB requires a CVE ID in order to pull vulnerability data and references from the CVE list and the National Vulnerability Database. If available, please supply below:
