CVE-2021-25216 Information

Description

In BIND 9.5.0 -> 9.11.29 9.12.0 -> 9.16.13 and versions BIND 9.11.3-S1 -> 9.11.29-S1 and 9.16.8-S1 -> 9.16.13-S1 of BIND Supported Preview Edition as well as release versions 9.17.0 -> 9.17.1 of the BIND 9.17 development branch BIND servers are vulnerable if they are running an affected version and are configured to use GSS-TSIG features. In a configuration which uses BIND’s default settings the vulnerable code path is not exposed but a server can be rendered vulnerable by explicitly setting values for the tkey-gssapi-keytab or tkey-gssapi-credential configuration options. Although the default configuration is not vulnerable GSS-TSIG is frequently used in networks where BIND is integrated with Samba as well as in mixed-server environments that combine BIND servers with Active Directory domain controllers. For servers that meet these conditions the ISC SPNEGO implementation is vulnerable to various attacks depending on the CPU architecture for which BIND was built: For named binaries compiled for 64-bit platforms this flaw can be used to trigger a buffer over-read leading to a server crash. For named binaries compiled for 32-bit platforms this flaw can be used to trigger a server crash due to a buffer overflow and possibly also to achieve remote code execution. We have determined that standard SPNEGO implementations are available in the MIT and Heimdal Kerberos libraries which support a broad range of operating systems rendering the ISC implementation unnecessary and obsolete. Therefore to reduce the attack surface for BIND users we will be removing the ISC SPNEGO implementation in the April releases of BIND 9.11 and 9.16 (it had already been dropped from BIND 9.17). We would not normally remove something from a stable ESV (Extended Support Version) of BIND but since system libraries can replace the ISC SPNEGO implementation we have made an exception in this case for reasons of stability and security.

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Reference

https://kb.isc.org/v1/docs/cve-2021-25215 http://www.openwall.com/lists/oss-security/2021/04/29/1 http://www.openwall.com/lists/oss-security/2021/04/29/2 http://www.openwall.com/lists/oss-security/2021/04/29/3 http://www.openwall.com/lists/oss-security/2021/04/29/4 https://www.debian.org/security/2021/dsa-4909 https://lists.debian.org/debian-lts-announce/2021/05/msg00001.html https://security.netapp.com/advisory/ntap-20210521-0006/ https://www.zerodayinitiative.com/advisories/ZDI-21-657/ https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

9.8