CVE-2025-40775 DNS message with invalid TSIG causes an assertion failure
Remote attackers can crash the BIND DNS server by sending a message with an invalid TSIG algorithm, causing an assertion failure.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-40775?
CVE-2025-40775 is a high-severity denial of service vulnerability in ISC BIND 9, published on 21 May 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
When an incoming DNS protocol message includes a Transaction Signature (TSIG), BIND always checks it. If the TSIG contains an invalid value in the algorithm field, BIND immediately aborts with an assertion failure. This issue affects BIND 9 versions 9.20.0 through 9.20.8 and 9.21.0 through 9.21.7.
Weakness: CWE-232
Which versions are affected by CVE-2025-40775?
Linux distribution packages (1)
bind openSUSE:Tumbleweed | All versions | 9.20.9-1.1 |
How do I fix CVE-2025-40775?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-40775 being exploited?
There is no known exploitation of CVE-2025-40775 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as ALPINE-CVE-2025-40775, AZL-61972, BELL-CVE-2025-40775, DEBIAN-CVE-2025-40775, GHSA-gqgx-hgvf-f75f, USN-7526-1 and 1 more.