CVE-2026-19033 Unauthenticated IXFR deltas are applied to the live zone before TSIG verification
Attackers can inject unauthorized zone data into secondary DNS servers by exploiting a race condition in TSIG verification during IXFR transfers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-19033?
CVE-2026-19033 is a medium-severity missing authorization vulnerability in ISC BIND 9, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
For a secondary zone with transfers restricted by TSIG, `named` may start to serve the data provided in a zone transfer before the final message with the TSIG signature arrives. This could allow an attacker that does not actually possess a valid TSIG signature to send unauthorized zone contents to a secondary server. Although no TSIG signature ever arrives, `named` does not rollback to the pre-transfer state. To exploit the vulnerability, the transfer must be a multi-message TCP IXFR, as described by RFC 8945. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.
Weakness: CWE-349
Which versions are affected by CVE-2026-19033?
How do I fix CVE-2026-19033?
Apply the vendor's patch.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-19033 being exploited?
There is no known exploitation of CVE-2026-19033 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-19033, AZL-103119, BELL-CVE-2026-19033, DEBIAN-CVE-2026-19033, ECHO-65a7-407e-b7bc, GHSA-r7m2-338w-h24g and 4 more.