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CISA KEV · ACTIVELY EXPLOITED
MEDIUM severity

CVE-2009-2055

MEDIUM

CVE-2009-2055 is a medium-severity (CVSS 5.9) Improper Input Validation vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2022-03-25) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.

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.

Published
Updated
Affected
1 product
Patched
See advisory
Exploits
2 known
Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

  • Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2022-03-25. Federal agencies were required to remediate by 2022-04-15.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2009-2055.

EPSS Exploitation Probability

via FIRST.org ↗
3.3%probability of exploitation in next 30 days
Lower Risk-0.01%
Lower risk than most CVEs89th percentile — riskier than 89% of all scored CVEsHighest risk
0.00%1.40%2.80%4.20%0.4%0.8%0.8%3.3%3.3%Apr 26Jun 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2009-2055 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

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.

Affected Products

1 product · 19 configurations
OS
ios xrcisco
19 versions
3.43.4.03.4.13.4.23.4.33.53.5.23.5.33.5.43.6.03.6.13.6.2
Exploits & PoCs
2

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Cisco IOS XR 3.4.0 through 3.8.1 allows remote attackers to cause a deni…

nvd.nist.govNVDAug 2009

Cisco IOS XR 3.4.0 through 3.8.1 allows remote attackers to cause a deni…

cisa.govCISAMar 2022

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Remediation status

    No fixed release is recorded for CVE-2009-2055 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

  3. Mitigate without a patch

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

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.
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CVE-2009-2055: Medium 5.9 (KEV)