CVE-2026-5947CWE-362CWE-367CWE-416

CVE-2026-5947

High · published May 20, 2026

CVSS v3.1
7.5
EPSS
1%
Percentile
56.1
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS v4.0
Not supplied
EPSS
0.00799 · 56.1th percentile
Weaknesses
CWE-362 · Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition'); CWE-367 · Time-of-check Time-of-use (TOCTOU) Race Condition; CWE-416 · Use After Free
Published
2026-05-20T17:16Z
Affected products (2)
ProductVersionsFixed in
isc/bind≥ 9.20.0, < 9.20.239.20.23
isc/bind≥ 9.21.0, < 9.21.229.21.22
References (7)
https://downloads.isc.org/isc/bind9/9.20.23 · [email protected]https://downloads.isc.org/isc/bind9/9.21.22 · [email protected]https://kb.isc.org/docs/cve-2026-5947 · [email protected]https://access.redhat.com/errata/RHSA-2026:7412 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46chttps://access.redhat.com/security/cve/CVE-2026-5947 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46chttps://bugzilla.redhat.com/show_bug.cgi?id=2479772 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46chttps://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5947.json · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
EPSS history
Timeline
  • 20 MAY 13:10Z
    SIG(0) validation during query flood may lead to undefined behavior
    cvelistv5