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Ios XrOperating system · Cisco

CVE-2013-5503

HIGH · 7.8 CVSS v2.0 Published 2013-10-02
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
87/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The UDP process in Cisco IOS XR 4.3.1 does not free packet memory upon detecting full packet queues, which allows remote attackers to cause a denial of service (memory consumption) via UDP packets to listening ports, aka Bug ID CSCue69413.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In Cisco IOS XR 4.3.1, the UDP process fails to release packet memory when it detects that packet queues have become full. This causes a memory leak that accumulates with each UDP packet sent to listening ports on the device, eventually leading to memory exhaustion and denial of service.

MitigationApply the relevant Cisco IOS XR patch or upgrade to a fixed version. If immediate patching is not feasible, implement access controls or rate limiting on upstream network devices to restrict UDP traffic destined for the affected system.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Ios XrOperating system
Affected:= 4.3.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Authentication
None
Confidentiality
None
Integrity
None
Availability
Complete

AV:N/AC:L/Au:N/C:N/I:N/A:C

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the Cisco IOS XR version
    Run 'show version' or 'show install active' from the IOS XR CLI to display the installed software version
    Affected if The displayed version is exactly 4.3.1
  2. Confirm UDP process is running
    Run 'show process memory | include UDP' or 'show udp statistics' to verify the UDP process is active and consuming memory
    Affected if The UDP process is running and memory usage is visible in the process list
  3. Check for symptoms of memory exhaustion
    Run 'show memory summary' or 'show process memory' to examine available system memory and observe if heap memory is depleting over time
    Affected if System memory shows progressive depletion, particularly in the UDP process memory area, with no recovery after traffic ceases

The environment is affected only if running exactly Cisco IOS XR version 4.3.1, the UDP process is active, and memory depletion is observed over time during normal UDP traffic operations.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the relevant Cisco IOS XR patch or upgrade to a fixed version. If immediate patching is not feasible, implement access controls or rate limiting on upstream network devices to restrict UDP traffic destined for the affected system.

Fix this in Ios Xr Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,690
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2013-5503 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data