Reachable assertion in ISC BIND - CVE-2025-40777
Published: July 17, 2025
Vulnerability identifier: #VU113026
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2025-40777
CWE-ID: CWE-617
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: ISC
Affected software:
ISC BIND
ISC BIND
Detailed vulnerability description
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to a reachable assertion when named caching resolver is configured with "serve-stale-enable=yes" and "stale-answer-client-timeout=0". A remote attacker can supply a specially crafted CNAME chain in DNS response and perform a denial of service attack against the resolver.
How to mitigate CVE-2025-40777
Install updates from vendor's website.