CVE-2021-29492
Description
Envoy is a cloud-native edge/middle/service proxy. Envoy does not decode escaped slash sequences `%2F` and `%5C` in HTTP URL paths in versions 1.18.2 and before. A remote attacker may craft a path with escaped slashes, e.g. `/something%2F..%2Fadmin`, to bypass access control, e.g. a block on `/admin`. A backend server could then decode slash sequences and normalize path and provide an attacker access beyond the scope provided for by the access control policy. ### Impact Escalation of Privileges when using RBAC or JWT filters with enforcement based on URL path. Users with back end servers that interpret `%2F` and `/` and `%5C` and `\` interchangeably are impacted. ### Attack Vector URL paths containing escaped slash characters delivered by untrusted client. Patches in versions 1.18.3, 1.17.3, 1.16.4, 1.15.5 contain new path normalization option to decode escaped slash characters. As a workaround, if back end servers treat `%2F` and `/` and `%5C` and `\` interchangeably and a URL path based access control is configured, one may reconfigure the back end server to not treat `%2F` and `/` and `%5C` and `\` interchangeably.
Related CPE's
References
CvssV3 impact
BaseSeverity | CRITICAL |
ConfidentialityImpact | HIGH |
AttackComplexity | LOW |
Scope | UNCHANGED |
AttackVector | NETWORK |
AvailabilityImpact | HIGH |
IntegrityImpact | HIGH |
PrivilegesRequired | NONE |
BaseScore | 9.8 |
VectorString | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
Version | 3.1 |
UserInteraction | NONE |
CvssV2 impact
AccessComplexity | LOW |
ConfidentialityImpact | PARTIAL |
AvailabilityImpact | PARTIAL |
IntegrityImpact | PARTIAL |
BaseScore | 7.5 |
VectorString | AV:N/AC:L/Au:N/C:P/I:P/A:P |
Version | 2.0 |
AccessVector | NETWORK |
Authentication | NONE |