Security Resilience

CVE-2009-2055

Cisco Ios Xr 3.4 … 3.8.1

CISA KEVActive ExploitationEUVD Exploited
Published
19 August 2009
Modified
22 April 2026
KEV Added
25 March 2022
Patch / advisory
CVSS Score v3.1 5.9
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.033 88th percentile
Risk Priority 75 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2009-2055 is a medium-severity Improper Input Validation (CWE-20) vulnerability in Cisco Ios Xr. Its CVSS base score is 5.9 (Medium).

Operationally, ranked in the top 12% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

Cisco IOS XR versions 3.4.0 through 3.8.1 contain an input validation flaw (CWE-20) in the handling of BGP messages. The affected component is the BGP implementation within these IOS XR releases, which fails to properly process UPDATE messages containing an invalid attribute.

Remote attackers can exploit the issue by sending a crafted BGP UPDATE message over an established session. Successful exploitation resets the BGP session, resulting in a denial of service that disrupts routing without requiring authentication or user interaction. The attack was observed in the wild on 17 August 2009.

The Cisco security advisory at http://www.cisco.com/en/US/products/products_security_advisory09186a0080af150f.shtml and related notices on SecurityTracker describe available software updates that address the vulnerability. Operators are advised to apply the recommended IOS XR patches to eliminate exposure.

The flaw received a CVSS v3 score of 5.9, reflecting high attack complexity but significant availability impact on affected routers.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

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.

CWE(s)
KEV Date Added
25 March 2022

Related Threats

CVEs Like This One

CVE-2024-20406Same product: Cisco Ios Xr
CVE-2010-3035Same product: Cisco Ios Xrboth on KEV
CVE-2018-0125Same vendor: Ciscoboth on KEV
CVE-2025-20393Same vendor: Ciscoboth on KEV
CVE-2024-20319Same product: Cisco Ios Xr
CVE-2017-12319Same vendor: Ciscoboth on KEV
CVE-2017-3881Same vendor: Ciscoboth on KEV
CVE-2018-0159Same vendor: Ciscoboth on KEV
CVE-2023-20190Same product: Cisco Ios Xr
CVE-2024-20489Same product: Cisco Ios Xr

Affected Assets

cisco
ios xr
3.4, 3.4.0, 3.4.1, 3.4.2, 3.4.3

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-20

Security testing and developer training directly verify and enforce proper input validation, reducing exploitability of injection and malformed-data weaknesses.

addresses: CWE-20

Security testing and evaluation at multiple SDLC stages directly detects missing or flawed input validation, with the required remediation process ensuring fixes are applied.

addresses: CWE-20

Directly implements checks on information inputs to reject invalid data before processing.

addresses: CWE-20

Spam protection mechanisms perform filtering and detection on inbound/outbound messages, directly compensating for missing or weak input validation of unsolicited content.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

blocks

A.8.25 mandates security requirements, secure coding guidelines, checkpoints, testing (incl. code scans) and developer training in the SDLC, which reaches a slice of input validation defects but leaves the majority (incomplete enforcement, second-order inputs, parser differentials, post-validation canonicalization) unaddressed as in the SA-3 and A.8.28 anchors.

blocks

Mandating input controls that include integrity checks and input validation ensures that untrusted data is examined before use, blocking the root cause of many injection and malformed-data weaknesses.

blocks

Security-by-design principles explicitly call for data validation and sanitization at every layer, reducing the chance that malformed or malicious input will be processed without scrutiny.

prevents

Requiring language-specific secure coding standards, peer review, SAST and documented mitigation of common programming errors forces validation of all inputs before they are trusted.

finds

Testing against a defined set of requirements and using code review plus vulnerability scanning forces validation of inputs and handling of unanticipated conditions, reducing the chance that malformed data will be accepted.

Hardening callouts derived

DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.

  • No fine-grained STIG row for CWE-20, a class-level weakness, and none of its children carries one either.

References