---
id: "CVE-2009-2055"
kind: "vulnerability"
aliases: ["CVE-2009-2055"]
title: "Cisco IOS XR: Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service Vulnerability"
severity: "high"
cvss: 5.9
epss: 0.03314
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Cisco IOS XR", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["bgp", "cisco", "exploited", "infrastructure", "ios-xr", "network-operators"]
not_affected_if: ["bgp-not-configured", "non-ios-xr-platform"]
published_at: "2009-08-19T17:30:01+00:00"
first_seen_at: "2026-10-23T19:11:52+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2009-2055", "first_seen_at": "2026-10-23T19:11:52+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2009-2055", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2009-2055", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Cisco IOS XR: Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service Vulnerability

Cisco IOS XR routers running BGP can be crashed or disrupted by a remote attacker sending crafted traffic. The attacker gets denial of service, not code execution or data access.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Cisco IOS XR affected ? fixed ?

## Fix

Apply the Cisco IOS XR update per the vendor advisory (CISA required action: apply updates per vendor instructions); the fixed version is unknown from the sources.

## Timeline

- 2026-10-23T19:11:52+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2009-2055
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2009-2055
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2009-2055

## From the sources

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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_