Ios XrOperating system · Cisco
CVE-2016-1376
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 · uneditedCisco IOS XR 4.2.3, 4.3.0, 4.3.4, and 5.3.1 on ASR 9000 devices allows remote attackers to cause a denial of service (CRC and symbol errors, and interface flap) via crafted bit patterns in packets, aka Bug ID CSCuv78548.
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 Cisco IOS XR software on ASR 9000 routers allows remote attackers to cause denial of service by sending specially crafted packets containing specific bit patterns. These packets trigger CRC errors and symbol errors on affected interfaces, causing them to flap (go down/up repeatedly).
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
= 4.2.3= 4.3.0= 4.3.4= 5.3.1CVSS 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
- Low
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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 platform' or 'show version' to confirm the hardware is a Cisco ASR 9000 series routerAffected if Device is an ASR 9000 series router
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Determine the IOS XR versionRun 'show version' and locate the IOS XR software version string (typically shown as XR VERSION like 4.2.3, 4.3.0, 4.3.4, or 5.3.1)Affected if The installed IOS XR version matches 4.2.3, 4.3.0, 4.3.4, or 5.3.1 exactly
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Check for CRC errors on interfacesRun 'show interfaces' or 'show controllers' for each active interface and look for CRC error counters incrementingAffected if CRC errors are being recorded on interfaces and correlate with incoming traffic from untrusted sources
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Detect interface flappingRun 'show interface' repeatedly or check logging for interfaces going down/up. Use 'show log' to review recent interface state changesAffected if Interfaces are experiencing repeated flaps (going down and up) without manual intervention or hardware issues
The environment is affected if running Cisco IOS XR versions 4.2.3, 4.3.0, 4.3.4, or 5.3.1 on an ASR 9000 router and observing CRC errors causing interface flapping.
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 dataApply the appropriate Cisco IOS XR software update or patch that addresses CSCuv78548. If no patch is immediately available, consider network segmentation or traffic filtering to limit exposure to untrusted sources.
Fix this in Ios Xr
Scoped from the published advisory
- Consultation6.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-1376 — 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-2016-1376 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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