CVE-2021-21240
Description
An uncontrolled resource consumption flaw as found in python-httplib2, due to a flawed regular expression used while parsing the WWW-Authenticate header in an HTTP response. This flaw allows a malicious or compromised server to reply with a crafted sequence of characters in the WWW-Authenticate header, leading to a denial of service of the httplib2 client accessing the server. The highest threat from this vulnerability is to system availability.
Statement
This flaw has been rated as having a security impact of Low, because it requires a malicious or compromised server in order to be exploited, and it only affects the HTTP client. In Red Hat OpenStack Platform 13, because the flaw has a lower impact and the fix would require a substantial amount of development, no update will be provided at this time for the RHOSP 13 python-httplib2 package.
Mitigation
Use strict mode to parse WWW-Authenticate headers. This can be done by setting `httplib2.USE_WWW_AUTH_STRICT_PARSING = True`. Please note, however, that strict mode might lead to bad results in case of ill-formed header values.
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 | 7.5 | 7.5 | 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 | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
If an attacker can trigger the allocation of the limited resources, but the number or size of the resources is not controlled, then the most common result is denial of service. This would prevent valid users from accessing the product, and it could potentially have an impact on the surrounding environment, i.e., the product may slow down, crash due to unhandled errors, or lock out legitimate users. For example, a memory exhaustion attack against an application could slow down the application as well as its host operating system.
Access Control,Other
Technical Impact: Bypass Protection Mechanism; Other
In some cases it may be possible to force the product to "fail open" in the event of resource exhaustion. The state of the product -- and possibly the security functionality - may then be compromised.
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