CVE-2021-29492
high · 8.1Envoy 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.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Weaknesses
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| envoyproxy | envoy | < 1.15.5 |
| envoyproxy | envoy | >= 1.16.0, < 1.16.4 |
| envoyproxy | envoy | >= 1.17.0, < 1.17.3 |
| envoyproxy | envoy | >= 1.18.0, < 1.18.3 |
Check a specific version with /api/v1/cve/match.
References
Query this programmatically:
curl https://evil-db.io/api/v1/cve/CVE-2021-29492