Description
Undefined behavior may result due to a race condition leading to a use-after-free violation. If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature. If, during that validation, the "recursive-clients" limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected.
Metrics
CVSS 3.1 5.9/10
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HWeakness enumeration
Affected software
| Vendor | Product | Versions |
|---|---|---|
| ISC | BIND 9 | >= 9.20.0, <= 9.20.22; >= 9.21.0, <= 9.21.21; >= 9.20.9-S1, <= 9.20.22-S1 |
| Red Hat | Red Hat Hardened Images | — |
| Red Hat | Red Hat Enterprise Linux 10 | — |
| Red Hat | Red Hat Enterprise Linux 6 | — |
| Red Hat | Red Hat Enterprise Linux 7 | — |
| Red Hat | Red Hat Enterprise Linux 8 | — |
| Red Hat | Red Hat Enterprise Linux 8 | — |
| Red Hat | Red Hat Enterprise Linux 9 | — |
| Red Hat | Red Hat Enterprise Linux 9 | — |
| Red Hat | Red Hat Enterprise Linux 9 | — |
| Red Hat | Red Hat OpenShift Container Platform 4 | — |
References
- https://downloads.isc.org/isc/bind9/9.20.23Patch
- https://downloads.isc.org/isc/bind9/9.21.22Patch
- https://kb.isc.org/docs/cve-2026-5947Vendor Advisory
- https://access.redhat.com/errata/RHSA-2026:7412
- https://access.redhat.com/security/cve/CVE-2026-5947
- https://bugzilla.redhat.com/show_bug.cgi?id=2479772
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5947.json
Timeline
- Published
- May 20, 2026
- Last modified
- Aug 24, 2026
- NVD status
- Modified