dbcve.org
Ios XrOperating system · Cisco

CVE-2023-20049

HIGH · 7.5 CVSS v3.1 Published 2023-03-09
Fix available
A fix is available. Upgrade to 7.5.3 / 7.6.2 or later.
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 bidirectional forwarding detection (BFD) hardware offload feature of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers, ASR 9902 Compact High-Performance Routers, and ASR 9903 Compact High-Performance Routers could allow an unauthenticated, remote attacker to cause a line card to reset, resulting in a denial of service (DoS) condition. This vulnerability is due to the incorrect handling of malformed BFD packets that are received on line cards where the BFD hardware offload feature is enabled. An attacker could exploit this vulnerability by sending a crafted IPv4 BFD packet to an affected device. A successful exploit could allow the attacker to cause line card exceptions or a hard reset, resulting in loss of traffic over that line card while the line card reloads.

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

This is a denial of service vulnerability in Cisco IOS XR Software's bidirectional forwarding detection (BFD) hardware offload feature. When malformed IPv4 BFD packets are received on line cards where BFD hardware offload is enabled, the line card experiences exceptions that can lead to a hard reset, causing traffic loss while the card reloads. The attack is exploitable remotely by an unauthenticated attacker sending crafted BFD packets.

MitigationDisable BFD hardware offload on affected line cards until a Cisco patch is available; alternatively, filter or rate-limit BFD traffic at network edges to block malformed packets.

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:< 7.5.3>= 7.6, < 7.6.2= 7.7

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 Cisco IOS XR is running
    Identify the device OS by running 'show version' or checking the device prompt/model. This vulnerability affects only Cisco IOS XR, not IOS or IOS-XE.
    Affected if Device is not running Cisco IOS XR - this vulnerability does not apply
  2. Check the installed IOS XR version
    Run 'show version' and locate the version string (e.g., 7.5.2, 7.6.1, 7.7). Compare against affected ranges: < 7.5.3, >= 7.6 and < 7.6.2, or exactly 7.7.
    Affected if Version falls within < 7.5.3, >= 7.6 and < 7.6.2, or = 7.7
  3. Determine if BFD is configured
    Run 'show bfd summary' or 'show bfd session' to see if any BFD sessions exist on the device.
    Affected if No BFD sessions are configured - the vulnerability requires BFD to be active
  4. Check if BFD hardware offload is enabled
    Run 'show bfd hardware offload' or look for 'hw-offload' in 'show bfd session detail' output. Alternatively, check configuration with 'show running-config | include bfd' for 'hardware offload' keywords.
    Affected if BFD hardware offload is enabled on any interface - this is the required condition for exploitation

User is affected if running vulnerable IOS XR versions AND BFD hardware offload is enabled, as malformed IPv4 BFD packets can trigger the DoS condition.

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.

dbcve · scoped
Upgrade available Upgrade to 7.5.3 / 7.6.2 or later
Fixed in 7.5.37.6.2
Interim mitigation

Disable BFD hardware offload on affected line cards until a Cisco patch is available; alternatively, filter or rate-limit BFD traffic at network edges to block malformed packets.

Recommended fix High confidence

Upgrade to IOS XR 7.5.4 or later, 7.6.3 or later, or 7.8 or later

  1. 1. Identify the current Cisco IOS XR version on the affected ASR 9000 Series routers using 'show version' command
  2. 2. Confirm BFD hardware offload is enabled using 'show bfd hardware offload' or 'show bfd session' commands
  3. 3. If running affected version (< 7.5.3, >= 7.6 and < 7.6.2, or 7.7), plan for upgrade to a fixed release
  4. 4. Download the fixed IOS XR software version from Cisco (7.5.4 or later, 7.6.3 or later, or 7.8 or later) from Cisco's software download center
  5. 5. Follow standard Cisco IOS XR upgrade procedures: copy the new package to bootflash, configure boot variable if needed, and reload the router
  6. 6. After upgrade, verify the IOS XR version and BFD functionality using 'show version' and 'show bfd session'
  7. 7. Confirm the line card is operational and BFD sessions are stable
Caveat Standard IOS XR upgrade may cause brief service disruption during reload; ensure maintenance window is scheduled

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Ios Xr Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,440
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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-2023-20049 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