CVE-2026-5947SIG(0) validation during query flood may lead to undefined behavior
Updated under an hour ago ()
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It affects ISC BIND 9 and 4 other products. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-362, CWE-416, CWE-367
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- isc
- NVD analysis
- Modified
- Record last updated
- Sep 1, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
ISC BIND 9 isc:bind_9 (from the name) | from 9.20.0 through 9.20.22; from 9.21.0 through 9.21.21; from 9.20.9-S1 through 9.20.22-S1; from 9.18.28 through 9.18.49 not affected; from 9.18.28-S1 through 9.18.49-S1 not affected | CNA record |
Red Hat Red Hat Hardened Images redhat:hummingbird | from 9.18.48-1.1.hum1 not affected | CISA ADP |
Red Hat Red Hat Enterprise Linux 10 redhat:enterprise_linux | 10 | CISA ADP |
Red Hat Red Hat OpenShift Container Platform 4 redhat:openshift | 4 | CISA ADP |
isc bind isc:bind | from 9.20.0 before 9.20.23; from 9.21.0 before 9.21.22 | NVD |
References
- https://kb.isc.org/docs/cve-2026-5947vendor-advisory
- https://downloads.isc.org/isc/bind9/9.20.23patch
- https://downloads.isc.org/isc/bind9/9.21.22patch
- 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
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.