CVE-2026-19033 PUBLISHED

Unauthenticated IXFR deltas are applied to the live zone before TSIG verification

Assigner: isc
Reserved: 06.08.2026 Published: 16.09.2026 Updated: 16.09.2026

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.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L
CVSS Score: 6.5

Product Status

Vendor ISC
Product BIND 9
Versions Default: unaffected
  • affected from 9.11.0 to 9.18.50 (incl.)
  • affected from 9.20.0 to 9.20.27 (incl.)
  • affected from 9.21.0 to 9.21.25 (incl.)
  • affected from 9.11.3-S1 to 9.18.50-S1 (incl.)
  • affected from 9.20.9-S1 to 9.20.27-S1 (incl.)

Exploits

This flaw was discovered in internal testing. We are not aware of any active exploits.

Workarounds

No workarounds known.

Solutions

Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.29, 9.21.26, or 9.20.29-S1.

References

Problem Types

  • CWE-349 Acceptance of Extraneous Untrusted Data With Trusted Data CWE

Impacts

  • A successful attack may result in arbitrary attacker-supplied data being added to a zone.