CVE-2009-2055
MediumExploitedPublic exploitCisco 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 Aug 19, 2009 · Updated Apr 22, 2026
Key Facts
Patch immediately- CVE-2009-2055 is a medium-severity vulnerability (CVSS 5.9 v3.1) affecting IOS Xr (Cisco).
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Mar 25, 2022. Public exploit code is available.
- EPSS estimates a 3.3% probability of exploitation in the next 30 days.
- No fixed version is listed yet; check the vendor advisory for mitigations.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
5.9
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS (30-day exploit likelihood)
3.3%
Higher than 88.3% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2009-2055 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Mar 25, 2022 | Apr 15, 2022 | Not reported |
| Industry KEV feed | Mar 25, 2022 | Apr 15, 2022 | Not reported |
| CIRCL KEV | Mar 25, 2022 | Apr 15, 2022 | Not reported |
| ENISA EUVD | Mar 25, 2022 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
19 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| IOS XrCisco | 3.4, 3.4.0, 3.4.1, 3.4.2, 3.4.3, 3.5, 3.5.2, 3.5.3 | n/a |
Timeline
Publicly disclosed
Aug 19, 2009
Added to CISA KEV
Mar 25, 2022
Added to Industry KEV feed
Mar 25, 2022
Added to CIRCL KEV
Mar 25, 2022
Added to ENISA EUVD
Mar 25, 2022
Last updated
Apr 22, 2026
Weakness Type
- CWE-20 Improper Input Validation
References
- patch20090818 Cisco IOS XR Software Border Gateway Protocol Vulnerability
- exploitVulnCheck exploitation report
- other[nanog] 20090817 RE: Anyone else seeing "(invalid or corrupt AS path) 3 bytes E01100" ?
- other1022739
- otherhttps://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2009-2055
FAQ
Common 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.
Affected: IOS Xr (Cisco) versions 3.4, 3.4.0, 3.4.1, 3.4.2, 3.4.3, 3.5, 3.5.2, 3.5.3. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Mar 25, 2022.
Yes. It was added on Mar 25, 2022 with a federal remediation due date of Apr 15, 2022.
Public exploit code is available.
No fixed version is listed yet; check the vendor advisory for mitigations.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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