CVE-2021-29492
Description
An authorization bypass vulnerability was found in envoyproxy/envoy. An attacker can potentially craft an HTTP request that defines a certain pattern of escaped characters in the URI path (such as %2F, %2f, %5C or %5c), allowing them to bypass the envoy authorization service. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.3 | 8.3 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Changed | Changed | N/A |
| Confidentiality | Low | Low | N/A |
| Integrity Impact | Low | Low | N/A |
| Availability Impact | Low | Low | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
Red Hat CVSS v3 Score Explanation
S:C - Given that this vulnerability is in envoy and the vulnerability is bypassing authorization, the affected component and the impacted are different. For example, a service relying on the authorization provided by envoy will now be potentially vulnerable.
CIA:L - Given that the vulnerable component is in the proxy and may potentially give access to services behind, it is only Low as it's not a complete compromise of the CIA. For example it is very unlikely that a service alone relies upon envoy checking the HTTP headers solely for authorization/authentication.
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data; Read Files or Directories
An attacker could bypass intended access restrictions to read sensitive data, either by reading the data directly from a data store that is not correctly restricted, or by accessing insufficiently-protected, privileged functionality to read the data.
Integrity
Technical Impact: Modify Application Data; Modify Files or Directories
An attacker could bypass intended access restrictions to modify sensitive data, either by writing the data directly to a data store that is not correctly restricted, or by accessing insufficiently-protected, privileged functionality to write the data.
Access Control
Technical Impact: Gain Privileges or Assume Identity; Bypass Protection Mechanism
An attacker could bypass intended access restrictions to gain privileges by modifying or reading critical data directly, or by accessing privileged functionality.
Confidentiality,Integrity,Availability
Technical Impact: Execute Unauthorized Code or Commands
An attacker could use elevated privileges to execute unauthorized commands or code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
An attacker could gain unauthorized access to resources on the system and excessively consume those resources, leading to a denial of service.
Acknowledgements
Red Hat would like to thank the Envoy security team for reporting this issue.
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