#VU109620 Reachable assertion in ISC BIND - CVE-2025-40775

Vulnerability identifier: #VU109620

Vulnerability risk: Medium

CVSSv4.0: 7.7 [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/E:P/U:Green]

CVE-ID: CVE-2025-40775

CWE-ID: CWE-617

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
ISC BIND
Server applications / DNS servers

Vendor: ISC

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to a reachable assertion when handling transaction signature (TSIG) in incoming DNS messages. A remote attacker can send specially crafted DNS messages to the affected server and perform a denial of service (DoS) attack.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

ISC BIND: 9.20.0 - 9.21.7

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External links
https://kb.isc.org/docs/cve-2025-40775

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.