BIND 9: Improper Handling of Undefined Values
CVE-2025-40775 is a high-severity improper handling of undefined values vulnerability in BIND 9 from ISC, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected BIND 9 versions: 9.20.0 through 9.20.8; 9.21.0 through 9.21.7. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 15.4% chance of exploitation within 30 days, which is in the top 3.15% of all scored CVEs.
EPSS places it among the vulnerabilities most likely to be exploited soon.
What to do
- Check which version of BIND 9 you run against the affected versions below, and install the vendor's latest release.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| ISC | BIND 9 | 9.20.0 through 9.20.8; 9.21.0 through 9.21.7 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA (isc.org).
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Handling of Undefined Values
The product does not handle or incorrectly handles when a value is not defined or supported for the associated parameter, field, or argument name.
More Improper Handling of Undefined Values vulnerabilities (CWE-232)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in BIND 9
- 7.5 High severity
- 7.5 High severity
- 8.1 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
Recent Improper Handling of Undefined Values vulnerabilities
- 7.7 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
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