CVE-2021-29492

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.

• CVE ID
• CVE-2021-29492

• Assigner
• security-advisories@github.com

• Vulnerability Status
• Analyzed

• Published Version
• 2021-05-28T21:15:08

• Last Modified Date
• 2021-12-10T18:10:32

• Version
• 2.0

• Vector String
• AV:N/AC:L/Au:N/C:P/I:P/A:P

• Access Vector
• NETWORK

• Access Compatibility
• LOW

• Authentication
• NONE

• Confidentiality Impact
• PARTIAL

• Integrity Impact
• PARTIAL

• Availability Impact
• PARTIAL

• Base Score
• 7.5

• Severity
• HIGH

• Exploitability Score
• 10

• Impact Score
• 6.4

• Version
• 3.1

• Vector String
• CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

• Attack Vector
• NETWORK

• Attack Compatibility
• LOW

• Privileges Required
• NONE

• User Interaction
• NONE

• Scope
• CHANGED

• Confidentiality Impact
• LOW

• Availability Impact
• LOW

• Base Score
• 8.3

• Base Severity
• HIGH

• Exploitability Score
• 3.9

• Impact Score
• 3.7