title: A vulnerability in BIND's GSSAPI security policy negotiation can be targeted by a buffer overflow attack
description: 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 valid values for the tkey-gssapi-keytab or tkey-gssapi-credentialconfiguration 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. The most likely outcome of a successful exploitation of the vulnerability is a crash of the named process. However, remote code execution, while unproven, is theoretically possible. Affects: BIND 9.5.0 -> 9.11.27, 9.12.0 -> 9.16.11, and versions BIND 9.11.3-S1 -> 9.11.27-S1 and 9.16.8-S1 -> 9.16.11-S1 of BIND Supported Preview Edition. Also release versions 9.17.0 -> 9.17.1 of the BIND 9.17 development branch
problem types: BIND 9.5.0 -> 9.11.27, 9.12.0 -> 9.16.11, and versions BIND 9.11.3-S1 -> 9.11.27-S1 and 9.16.8-S1 -> 9.16.11-S1 of BIND Supported Preview Edition. Also release versions 9.17.0 -> 9.17.1 of the BIND 9.17 development branch:GSS-TSIG is an extension to the TSIG protocol which is intended to support the secure exchange of keys for use in verifying the authenticity of communications between parties on a network.  SPNEGO is a negotiation mechanism used by GSSAPI, the application protocol interface for GSS-TSIG.  The SPNEGO implementation used by BIND has been found to be vulnerable to a buffer overflow attack.
affected:
{
product: BIND9
vendor: ISC
versions:
status: affected, version: Open Source Branches 9.5 though 9.11 9.5.0 through versions before 9.11.28
status: affected, version: Open Source Branches 9.12 though 9.16 9.12.0 through versions before 9.16.12
status: affected, version: Supported Preview Branch 9.11-S 9.11.3-S1 through versions before 9.11.28-S1
status: affected, version: Supported Preview Branch 9.16-S 9.16.8-S1 through versions before 9.16.12-S1
status: affected, version: Development Branch 9.17 9.17.0 through versions before 9.17.2
}
metrics:
cvssV3_1: [
attackComplexity: HIGH
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 8.1
baseSeverity: HIGH
confidentialityImpact: HIGH
integrityImpact: HIGH
privilegesRequired: NONE
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
version: 3.1
]
solutions: Upgrade to the patched release most closely related to your current version of BIND:
BIND 9.11.28
BIND 9.16.12
BIND Supported Preview Edition is a special feature-preview branch of BIND provided to eligible ISC support customers.
BIND 9.11.28-S1
BIND 9.16.12-S1
Acknowledgments: ISC would like to thank an anonymous party, working in conjunction with Trend Micro Zero Day Initiative, for reporting this issue to us.
workarounds: This vulnerability only affects servers configured to use GSS-TSIG, most often to sign dynamic updates. If another mechanism can be used to authenticate updates, the vulnerability can be avoided by choosing not to enable the use of GSS-TSIG features.
On some platforms it may be possible to build a working BIND installation that is not vulnerable to CVE-2020-8625 by providing the --disable-isc-spnego command-line argument when running the ./configure script in the top level of the BIND source directory, before compiling and linking named.
Choosing to configure and build BIND without the ISC SPNEGO implementation does not produce a vulnerable BIND on any platform, but on platforms where GSSAPI support in the system is lacking, building without the ISC SPNEGO implementation may result in unusable GSSAPI features (such as an inability to use GSS-TSIG-signed DDNS updates).