Ios XrOperating system · Cisco
CVE-2020-26070
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 · uneditedA vulnerability in the ingress packet processing function of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper resource allocation when an affected device processes network traffic in software switching mode (punted). An attacker could exploit this vulnerability by sending specific streams of Layer 2 or Layer 3 protocol data units (PDUs) to an affected device. A successful exploit could cause the affected device to run out of buffer resources, which could make the device unable to process or forward traffic, resulting in a DoS condition. The device would need to be restarted to regain functionality.
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 · moderate confidenceA vulnerability in the ingress packet processing function of Cisco IOS XR Software on ASR 9000 Series routers allows an unauthenticated remote attacker to cause denial of service by sending specific Layer 2 or Layer 3 PDU streams. The vulnerability stems from improper resource allocation when the device processes traffic in software switching mode (punted), causing buffer exhaustion that makes the device unable to forward traffic until restarted.
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
< 6.7.2>= 7.1.0, < 7.1.2CVSS 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
- Changed
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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 checksWork through these to decide whether this CVE applies to you.
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Identify the device modelRun 'show version' or check the device chassis to confirm it is an ASR 9000 Series routerAffected if Device is not an ASR 9000 Series router, then it is not affected by this specific CVE
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Verify IOS XR software is runningRun 'show version' and confirm the operating system is Cisco IOS XRAffected if Device does not run IOS XR software, it is not affected
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Check the IOS XR versionRun 'show version' and locate the IOS XR release number (for example, 6.7.1 or 7.1.1)Affected if Version is less than 6.7.2 OR version is 7.1.0 through 7.1.2 (inclusive), then the device is running a vulnerable version
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Determine if software switching mode (punted traffic) is in useRun 'show controllers npu stats' or 'show punt cause' to check if the device is processing traffic in software switching mode rather than hardware forwardingAffected if The device is actively puntng traffic to the CPU for software processing, making it susceptible to the buffer exhaustion condition described in the CVE
A user is affected if they are running Cisco IOS XR on an ASR 9000 Series router with a version in the vulnerable range (< 6.7.2 or 7.1.0-7.1.2) AND the device is processing traffic in software switching mode (punted) where the resource allocation flaw can trigger buffer exhaustion.
Generated from the published advisory. Verify against your own configuration.
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 data6.7.27.1.2
Apply Cisco IOS XR software updates when available; consider network segmentation and ingress filtering to limit exposure to unauthenticated PDU streams targeting affected devices.
Fix this in Ios Xr
Scoped from the published advisory
- Consultation8.0 h
- Implementation12.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,608.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-26070 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-26070 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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