dbcve.org
Ios XrOperating system · Cisco

CVE-2025-20209

HIGH · 7.5 CVSS v3.1 Published 2025-03-12
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
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
A vulnerability in the Internet Key Exchange version 2 (IKEv2) function of Cisco IOS XR Software could allow an unauthenticated, remote attacker to prevent an affected device from processing any control plane UDP packets.  This vulnerability is due to improper handling of malformed IKEv2 packets. An attacker could exploit this vulnerability by sending malformed IKEv2 packets to an affected device. A successful exploit could allow the attacker to prevent the affected device from processing any control plane UDP packets, resulting in a denial of service (DoS) condition. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

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

A vulnerability in Cisco IOS XR Software's IKEv2 function allows unauthenticated remote attackers to cause denial of service by sending malformed IKEv2 packets, preventing the affected device from processing any control plane UDP packets.

MitigationApply the Cisco software update that addresses this vulnerability; there are no available workarounds.

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:= 6.5.1= 6.5.2= 6.5.3= 6.6.1= 6.6.2= 6.6.3= 6.6.25= 7.0.0= 7.0.1= 7.0.2= 7.1.1= 7.1.2

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
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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. Confirm the device runs Cisco IOS XR
    Log into the device CLI and run 'show version' to identify the operating system. Look for 'IOS XR' in the output.
    Affected if The device is not running Cisco IOS XR (the vulnerability only applies to IOS XR)
  2. Determine the installed IOS XR version
    Run 'show version' and locate the version number in the output (for example, 7.1.2, 6.6.3)
    Affected if The installed version matches any of: 6.5.1, 6.5.2, 6.5.3, 6.6.1, 6.6.2, 6.6.3, 6.6.25, 7.0.0, 7.0.1, 7.0.2, 7.1.1, or 7.1.2
  3. Verify IKEv2 is configured on the device
    Run 'show crypto ikev2 sa' or 'show crypto ikev2 session' to check for active IKEv2 security associations or sessions
    Affected if IKEv2 is actively configured or has active security associations, meaning the device can receive IKEv2 packets on UDP port 500 or 4500
  4. Confirm control plane UDP processing is impacted
    After receiving malformed IKEv2 packets, run 'show udp engines' or test control plane connectivity. The vulnerability prevents the device from processing any control plane UDP packets.
    Affected if The device stops processing control plane UDP traffic after receiving malformed IKEv2 packets

You are affected if your device runs Cisco IOS XR version 6.5.1 through 7.1.2 and has IKEv2 enabled, allowing malformed IKEv2 packets to cause denial of service on control plane UDP processing.

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 Cisco software update that addresses this vulnerability; there are no available workarounds.

Fix this in Ios Xr Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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Scan for this in your stack

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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-2025-20209 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