CVE-2021-25220
Description
A cache poisoning vulnerability was found in BIND when using forwarders. Bogus NS records supplied by the forwarders may be cached and used by name if it needs to recurse for any reason. This issue causes it to obtain and pass on potentially incorrect answers. This flaw allows a remote high privileged attacker to manipulate cache results with incorrect records, leading to queries made to the wrong servers, possibly resulting in false information received on the client's end.
Statement
Versions of BIND shipped with Red Hat Enterprise Linux 8, 9 are affected, because vulnerable code is present in our code base.
For RHEL-9, DHCP uses the vulnerable BIND 9 libraries (bind-9.11.14) for some services. Hence, it is affected as well.
Authoritative - Only BIND 9 servers are not vulnerable to this flaw.
Mitigation
If applicable, modify your configuration to either remove all forwarding or all possibility of recursion. Depending on your use case, it may be possible to use other zone types to replace forward zones.
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 | 6.8 | 6.8 | 6.8 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | Low |
| Privileges Required | High | High | High |
| User Interaction | None | None | None |
| Scope | Changed | Changed | Changed |
| Confidentiality | None | None | None |
| Integrity Impact | High | High | High |
| Availability Impact | None | None | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:N
Understanding the Weakness (CWE)
Integrity,Non-Repudiation,Access Control
Technical Impact: Unexpected State; Hide Activities; Bypass Protection Mechanism
An attacker could create HTTP messages to exploit a number of weaknesses including 1) the message can trick the web server to associate a URL with another URL's webpage and caching the contents of the webpage (web cache poisoning attack), 2) the message can be structured to bypass the firewall protection mechanisms and gain unauthorized access to a web application, and 3) the message can invoke a script or a page that returns client credentials (similar to a Cross Site Scripting attack).
Acknowledgements
Upstream acknowledges Baojun Liu (Network and Information Security Lab, Tsinghua University), Changgen Zou (Qi An Xin Group Corp), Chaoyi Lu (Network and Information Security Lab, Tsinghua University), and Xiang Li (Network and Information Security Lab, Tsinghua University) as the original reporters.
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