Reachable Assertion in ISC BIND - CVE-2021-25218
Published: August 18, 2021
Vulnerability identifier: #VU55974
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2021-25218
CWE-ID: CWE-617
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to a reachable assertion when sending large responses over UDP. If named attempts to respond over UDP
with a response that is larger than the current effective interface
maximum transmission unit (MTU), and if response-rate limiting (RRL) is
active, an assertion failure is triggered. A remote attacker can force named to trigger the assertion failure and perform a denial of service attack.
Affected software
ISC BIND
Fedora
bind
bind-dyndb-ldap
Fedora
bind
bind-dyndb-ldap
How to mitigate CVE-2021-25218
Install updates from vendor's website.
ISC BIND - addressed in versions 9.16.20, 9.16.20-S1, 9.17.17
bind - update to 9.16.20-2.fc34
bind-dyndb-ldap - update to 11.9-4.fc34
bind - update to 9.16.20-2.fc34
bind-dyndb-ldap - update to 11.9-4.fc34