CVE-2026-5947 | BDVDB-2026-334086 Detail
ISCBIND 9
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.
Impact#
The use of memory after it is freed is undefined ("dangling pointer"). The BIND process may abort with a segmentation violation or similar error. If memory from the discarded message has not been reused or reclaimed, the validation might proceed normally. Any kind of code execution from such an improper data read is unlikely.
Weaknesses#
References#
- https://kb.isc.org/docs/cve-2026-5947
- https://downloads.isc.org/isc/bind9/9.20.23
- https://downloads.isc.org/isc/bind9/9.21.22
- 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
- https://access.redhat.com/errata/RHSA-2026:7412
Exploit#
No public exploit known
History#
- Version 1Record published in the CVE List.
- Version 2Most recent update recorded in the CVE List.