CVE-2026-5947
CVE-2026-5947 — SIG(0) validation during query flood may lead to undefined behavior
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.
Published Updated Sources: cvelistV5, isc
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.
Exploitation
Unreported
no source claims exploitation
EPSS
1%
chance of exploitation in 30 days
CVSS base
7.5
HIGH
CISA SSVC assessment
Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.
Exploitation
None
none · proof-of-concept · active
Automatable
Yes
can an attacker script all four kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component
Affected scope
The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.
Every base score collected
Sources score independently and disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Source |
|---|---|---|---|---|---|
| 7.5 | CVSS 3.1 | HIGH | — | — | cvelistV5 |
Weakness & attack patterns
- CWE-362
- CWE-416
- CWE-367
References
7 on the record
- kb.isc.org/docs/cve-2026-5947
vendor-advisory
- downloads.isc.org/isc/bind9/9.20.23
patch
- downloads.isc.org/isc/bind9/9.21.22
patch
- access.redhat.com/security/cve/CVE-2026-5947
vdb-entry, x_refsource_REDHAT
- bugzilla.redhat.com/show_bug.cgi?id=2479772
issue-tracking, x_refsource_REDHAT
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5947.json
x_sadp-csaf-vex
- access.redhat.com/errata/RHSA-2026:7412
vendor-advisory, x_refsource_REDHAT
Elsewhere on this site
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.