# 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.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Sep 2026
- **Updated:** 17 Sep 2026
- **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, MINI-766w-m98m-h655, MINI-9384-cj2g-c4mq, MINI-9m6m-4j6p-853q, UBUNTU-CVE-2026-19033

## 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 (Acceptance of Extraneous Untrusted Data With Trusted Data)

## Which versions are affected by CVE-2026-19033?


## How do I fix CVE-2026-19033?

Apply the vendor's patch.

## Is CVE-2026-19033 being exploited?

There is no known exploitation of CVE-2026-19033 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-19033 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-19033 in the wild and no public exploit code.

Affected product: ISC BIND 9. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-19033/ (Markdown: https://insights.sbomify.com/CVE-2026-19033/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-19033
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-19033
- OSV: https://osv.dev/vulnerability/CVE-2026-19033

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-19033/
Summaries are generated and may contain mistakes; the official description above is the record.