# CVE-2021-25214: A broken inbound incremental zone update (IXFR) can cause named to terminate unexpectedly

> A remote attacker can cause the BIND DNS server to crash by sending a malformed IXFR request, resulting in a denial of service.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 Apr 2021
- **Updated:** 17 Sep 2024
- **Also known as:** ALPINE-CVE-2021-25214, ALSA-2021:4384, CLSA-2022-1643212135, DEBIAN-CVE-2021-25214, GHSA-pqmv-mqwc-wmr3, MGASA-2021-0275, RHSA-2021:3325, RHSA-2021:4384, RLSA-2021:4384, UBUNTU-CVE-2021-25214

## What is CVE-2021-25214?

CVE-2021-25214 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 29 Apr 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

In BIND 9.8.5 -> 9.8.8, 9.9.3 -> 9.11.29, 9.12.0 -> 9.16.13, and versions BIND 9.9.3-S1 -> 9.11.29-S1 and 9.16.8-S1 -> 9.16.13-S1 of BIND 9 Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.11 of the BIND 9.17 development branch, when a vulnerable version of named receives a malformed IXFR triggering the flaw described above, the named process will terminate due to a failed assertion the next time the transferred secondary zone is refreshed.

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2021-25214?

It affects 15 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `bind` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-chroot` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-devel` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-libs` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-libs-lite` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-license` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-lite-devel` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-pkcs11` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-pkcs11-devel` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-pkcs11-libs` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-pkcs11-utils` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-sdb` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-sdb-chroot` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind-utils` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `python3-bind` | AlmaLinux:8 | All versions | 32:9.11.26-6.el8 |
| `bind` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-chroot` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-devel` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-export-devel` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-export-libs` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-libs` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-libs-lite` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-license` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-lite-devel` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-pkcs11` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-pkcs11-devel` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-pkcs11-libs` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-pkcs11-utils` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-sdb` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-sdb-chroot` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-utils` | Red Hat:enterprise_linux:7::client | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind` | Red Hat:enterprise_linux:7::computenode | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-chroot` | Red Hat:enterprise_linux:7::computenode | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-debuginfo` | Red Hat:enterprise_linux:7::computenode | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-export-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-lite-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-pkcs11` | Red Hat:enterprise_linux:7::computenode | All versions | 32:9.11.4-26.P2.el7_9.7 |
| `bind-pkcs11-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 32:9.11.4-26.P2.el7_9.7 |

Products: Debian Debian Linux, Fedoraproject Fedora, Isc Bind, Netapp Active Iq Unified Manager, Netapp Aff 500f Firmware, Netapp Aff A250 Firmware, Netapp Cloud Backup, Netapp H300e Firmware, Netapp H300s Firmware, Netapp H410s Firmware, Netapp H500e Firmware, Netapp H500s Firmware, Netapp H700e Firmware, Netapp H700s Firmware, Siemens Sinec Infrastructure Network Services.

## How do I fix CVE-2021-25214?

Upgrade to a fixed version.

## Is CVE-2021-25214 being exploited?

There is no known exploitation of CVE-2021-25214 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-25214 and fix it if it is affected.

What it is: CVE-2021-25214 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 29 Apr 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-25214 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2021-25214/ (Markdown: https://insights.sbomify.com/CVE-2021-25214/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-25214
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-25214
- OSV: https://osv.dev/vulnerability/CVE-2021-25214

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-25214/
Summaries are generated and may contain mistakes; the official description above is the record.