Log in Start free

Vulnerability · Published Apr 29, 2021 · Assigned by isc

CVE-2021-25216A second vulnerability in BIND's GSSAPI security policy negotiation can be targeted by a buffer overflow attack

High 8.1

In plain English

A high-severity security flaw in BIND9 from ISC. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 83.0% (higher than 99.7% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.1High
Exploit odds (30 days)83.0%top 0.3% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.20bind9.16.15-r0ALPINE-CVE-2021-25216
Alpine:v3.21bind9.16.15-r0ALPINE-CVE-2021-25216
Alpine:v3.22bind9.16.15-r0ALPINE-CVE-2021-25216
Alpine:v3.23bind9.16.15-r0ALPINE-CVE-2021-25216
Alpine:v3.24bind9.16.15-r0ALPINE-CVE-2021-25216
Debian:12bind91:9.16.15-1DEBIAN-CVE-2021-25216
Debian:13bind91:9.16.15-1DEBIAN-CVE-2021-25216
Debian:14bind91:9.16.15-1DEBIAN-CVE-2021-25216

Affected products (as reported)

VendorProductVersions
ISC BIND9 Open Source Branches 9.5 though 9.11 9.5.0 through versions before 9.11.31Open Source Branches 9.12 though 9.16 9.12.0 through versions before 9.16.14Supported Preview Branch 9.11-S 9.11.3-S1 through versions before 9.11.31-S1Supported Preview Branch 9.16-S 9.16.8-S1 through versions before 9.16.14-S1Development Branch 9.17 9.17.0 through versions before 9.17.2

References