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.
References
| Link | Resource |
|---|---|
| https://github.com/envoyproxy/envoy/security/advisories/GHSA-4987-27fx-x6cf | Mitigation Third Party Advisory |
Configurations
Configuration 1 (hide)
|
History
10 Dec 2021, 18:10
| Type | Values Removed | Values Added |
|---|---|---|
| CVSS |
v2 : v3 : |
v2 : 7.5
v3 : 8.3 |
10 Jun 2021, 14:30
| Type | Values Removed | Values Added |
|---|---|---|
| References | (CONFIRM) https://github.com/envoyproxy/envoy/security/advisories/GHSA-4987-27fx-x6cf - Mitigation, Third Party Advisory | |
| CPE | cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* | |
| CVSS |
v2 : v3 : |
v2 : 7.5
v3 : 9.8 |
07 Jun 2021, 12:15
| Type | Values Removed | Values Added |
|---|---|---|
| Summary | 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. |
28 May 2021, 22:15
| Type | Values Removed | Values Added |
|---|---|---|
| Summary | ### Description 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 Envoy versions 1.18.3, 1.17.3, 1.16.4, 1.15.5 contain new path normalization option to decode escaped slash characters. ### Workarounds If back end servers treat `%2F` and `/` and `%5C` and `\` interchangeably and a URL path based access control is configured, we recommend reconfiguring back end server to not treat `%2F` and `/` and `%5C` and `\` interchangeably if feasible. ### Credit Ruilin Yang (ruilin.yrl@gmail.com) ### References https://blog.envoyproxy.io https://github.com/envoyproxy/envoy/releases ### For more information If you have any questions or comments about this advisory: * Open an issue in [Envoy repo](https://github.com/envoyproxy/envoy/issues) * Email us at [envoy-security](mailto:envoy-security@googlegroups.com) | |
| CWE | CWE-22 |
28 May 2021, 21:15
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2021-05-28 21:15
Updated : 2023-12-10 13:55
NVD link : CVE-2021-29492
Mitre link : CVE-2021-29492
CVE.ORG link : CVE-2021-29492
JSON object : View
Products Affected
envoyproxy
- envoy
CWE
CWE-22
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')