CVE-2025-40777
published 2025-07-16CVE-2025-40777: If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable value other…
PriorityP342high7.5CVSS 3.1
AVNACLPRNUINSUCNINAH
EPSS
0.88%
55.3th percentile
If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable value other than `disabled`), and if the resolver, in the process of resolving a query, encounters a CNAME chain involving a specific combination of cached or authoritative records, the daemon will abort with an assertion failure.
This issue affects BIND 9 versions 9.20.0 through 9.20.10, 9.21.0 through 9.21.9, and 9.20.9-S1 through 9.20.10-S1.
Affected
9 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | bind9 | < bind9 1:9.20.11-1 (forky) | bind9 1:9.20.11-1 (forky) |
| isc | bind | >= 0 < 9.20.11-r0 | 9.20.11-r0 |
| isc | bind | >= 0 < 9.20.11-r0 | 9.20.11-r0 |
| isc | bind9 | >= 0 < 1:9.20.11-1 | 1:9.20.11-1 |
| isc | bind9 | >= 0 < 1:9.20.11-1 | 1:9.20.11-1 |
| isc | bind_9 | 9.20.0 – 9.20.10 | — |
| isc | bind_9 | 9.20.9-S1 – 9.20.10-S1 | — |
| isc | bind_9 | 9.21.0 – 9.21.9 | — |
| msrc | azl3_bind_9.20.11-1_on_azure_linux_3.0 | — | — |
CVSS provenance
nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
osv7.5HIGH
vendor_debian7.5HIGH
vendor_msrc7.5HIGH
vendor_redhat7.5HIGH
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OSV
CVE-2025-40777: If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable val
osv·2025-07-16·CVSS 7.5
CVE-2025-40777 [HIGH] CVE-2025-40777: If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable val
If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable value other than `disabled`), and if the resolver, in the process of resolving a query, encounters a CNAME chain involving a specific combination of cached or authoritative records, the daemon will abort with an assertion failure.
This issue affects BIND 9 versions 9.20.0 through 9.20.10, 9.21.0 through 9.21.9, and 9.20.9-S1 through 9.20.10-S1.
GHSA
GHSA-4x4c-8qp9-8ggh: If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable val
ghsa_unreviewed·2025-07-16
CVE-2025-40777 [HIGH] CWE-617 GHSA-4x4c-8qp9-8ggh: If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable val
If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable value other than `disabled`), and if the resolver, in the process of resolving a query, encounters a CNAME chain involving a specific combination of cached or authoritative records, the daemon will abort with an assertion failure.
This issue affects BIND 9 versions 9.20.0 through 9.20.10, 9.21.0 through 9.21.9, and 9.20.9-S1 through 9.20.10-S1.
OSV
CVE-2025-40777: If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable val
osv·2025-07-16·CVSS 7.5
CVE-2025-40777 [HIGH] CVE-2025-40777: If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable val
If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable value other than `disabled`), and if the resolver, in the process of resolving a query, encounters a CNAME chain involving a specific combination of cached or authoritative records, the daemon will abort with an assertion failure. This issue affects BIND 9 versions 9.20.0 through 9.20.10, 9.21.0 through 9.21.9, and 9.20.9-S1 through 9.20.10-S1.
Ubuntu
Bind vulnerability
vendor_ubuntu·2025-07-16
CVE-2025-40777 Bind vulnerability
Title: Bind vulnerability
Summary: Bind could be made to crash if it received specially crafted network
traffic.
It was discovered that Bind incorrectly handled configurations where the
stale-answer-client-timeout option is set to 0. A remote attacker could
possibly use this issue to cause Bind to crash, resulting in a denial of
service.
Instructions: In general, a standard system update will make all the necessary changes.
Red Hat
bind: bind assertion failure
vendor_redhat·2025-07-16·CVSS 7.5
CVE-2025-40777 [HIGH] CWE-617 bind: bind assertion failure
bind: bind assertion failure
If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable value other than `disabled`), and if the resolver, in the process of resolving a query, encounters a CNAME chain involving a specific combination of cached or authoritative records, the daemon will abort with an assertion failure.
This issue affects BIND 9 versions 9.20.0 through 9.20.10, 9.21.0 through 9.21.9, and 9.20.9-S1 through 9.20.10-S1.
An assertion failure flaw has been discovered in bind. If a `named` caching resolver is configured with `serve-stale-enable`: `yes`, and with `stale-answer-client-timeout` set to `0`, and if the resolver, in the process of resolving a query, encounters a CNAME chain involvin
Microsoft
A possible assertion failure when 'stale-answer-client-timeout' is set to '0'
vendor_msrc·2025-07-08·CVSS 7.5
CVE-2025-40777 [HIGH] CWE-617 A possible assertion failure when 'stale-answer-client-timeout' is set to '0'
A possible assertion failure when 'stale-answer-client-timeout' is set to '0'
FAQ: Is Azure Linux the only Microsoft product that includes this open-source library and is therefore potentially affected by this vulnerability?
One of the main benefits to our customers who choose to use the Azure Linux distro is the commitment to keep it up to date with the most recent and most secure versions of the open source libraries with which the distro is composed. Microsoft is committed to transparency in this work which is why we began publishing CSAF/VEX in October 2025. See this blog post for more information. If impact to additional products is identified, we will update the CVE to reflect this.
Mariner: Mariner
isc: isc
Customer Action Required: Yes
Remediation: CBL-Mariner Releases
Refere
Debian
CVE-2025-40777: bind9 - If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and...
vendor_debian·2025·CVSS 7.5
CVE-2025-40777 [HIGH] CVE-2025-40777: bind9 - If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and...
If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable value other than `disabled`), and if the resolver, in the process of resolving a query, encounters a CNAME chain involving a specific combination of cached or authoritative records, the daemon will abort with an assertion failure. This issue affects BIND 9 versions 9.20.0 through 9.20.10, 9.21.0 through 9.21.9, and 9.20.9-S1 through 9.20.10-S1.
Scope: local
bookworm: open
bullseye: open
forky: resolved (fixed in 1:9.20.11-1)
sid: resolved (fixed in 1:9.20.11-1)
trixie: resolved (fixed in 1:9.20.11-1)
No detection rules found.
No public exploits indexed.
No writeups or analysis indexed.
2025-07-16
Published