CVE-2026-5947: ISC BIND 9 · Race Condition
Affects ISC BIND 9Source CVE Database V5
Not known to be exploited · CVSS 7.5 High : upgrade to 9.21.22 or 9.20.23 soon.
Data as of 30 Oct 2026, 06:59 UTC
- EPSS
- 1.3% chance of exploitation in 30 days – higher than 72% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 9.21.22, 9.20.23
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 20 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
What to do
Upgrade isc/bind9 to 9.21.22 or 9.20.23.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| ISCBIND 9 | Affected
| Fixed in– |
GitHubisc/bind9pkg:github/isc/bind9Other threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
The Red Hat advisories referencing this CVE do not currently list a fix or updated packages addressing this vulnerability. If you cannot patch yet, consider limiting exposure to query floods that might trigger the recursive-clients limit or implement network-level protections to mitigate query floods.
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.
References
- kb.isc.org/docs/cve-2026-5947 (opens in a new tab)
- downloads.isc.org/isc/bind9/9.20.23 (opens in a new tab)
- downloads.isc.org/isc/bind9/9.21.22 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-5947 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2479772 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5947.json (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:7412 (opens in a new tab)