dbcve.org
Ios XrOperating system · Cisco

CVE-2024-20327

HIGH · 7.4 CVSS v3.1 Published 2024-03-13
Fix available
A fix is available. Upgrade to 7.9.21 / 7.10.1 or later.
See remediation →
79/100
Remediation priority · High
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 PPP over Ethernet (PPPoE) termination feature of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, adjacent attacker to crash the ppp_ma process, resulting in a denial of service (DoS) condition. This vulnerability is due to the improper handling of malformed PPPoE packets that are received on a router that is running Broadband Network Gateway (BNG) functionality with PPPoE termination on a Lightspeed-based or Lightspeed-Plus-based line card. An attacker could exploit this vulnerability by sending a crafted PPPoE packet to an affected line card interface that does not terminate PPPoE. A successful exploit could allow the attacker to crash the ppp_ma process, resulting in a DoS condition for PPPoE traffic across the router.

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 on ASR 9000 Series routers allows an adjacent, unauthenticated attacker to crash the ppp_ma process by sending malformed PPPoE packets to a line card interface that is not terminating PPPoE, even when the router is running BNG functionality with PPPoE termination on Lightspeed or Lightspeed-Plus line cards. The improper handling of these crafted packets causes a denial of service for all PPPoE traffic across the router.

MitigationApply the Cisco software update for CVE-2024-20327 when available; until then, consider network segmentation to limit adjacent attacker access to affected interfaces.

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:< 7.9.21>= 7.10, < 7.10.1>= 7.11, < 7.11.1

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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/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 checks

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

  1. Identify the router model
    Execute 'show platform' or 'show version' and confirm the hardware is an ASR 9000 Series router
    Affected if Device is not an ASR 9000 Series router - the vulnerability does not apply
  2. Check the IOS XR software version
    Run 'show version' and locate the IOS XR release number (for example, 7.9.15, 7.10.0, 7.11.0)
    Affected if Version is less than 7.9.21, OR falls between 7.10.0 and 7.10.1 (excluding 7.10.1), OR falls between 7.11.0 and 7.11.1 (excluding 7.11.1)
  3. Verify BNG functionality is enabled
    Run 'show running-config | include bng' or 'show bng session summary' to determine if Broadband Network Gateway (BNG) is configured on the router
    Affected if BNG is not enabled - the ppp_ma process is not running and the vulnerability cannot be triggered
  4. Confirm PPPoE termination is configured
    Run 'show pppoe session' or 'show running-config | include pppoe' to check for active PPPoE sessions or PPPoE-related interface configuration
    Affected if No PPPoE termination exists on the router - the malformed packets cannot reach the vulnerable code path
  5. Identify line card type handling PPPoE
    Run 'show controller npu' or 'show hw-module location all' to identify the line card types (Lightspeed or Lightspeed-Plus) that are processing PPPoE interfaces
    Affected if PPPoE traffic is not terminated on Lightspeed or Lightspeed-Plus line cards - the specific vulnerability condition is not met

The environment is affected only if the router is an ASR 9000 running a vulnerable IOS XR version (per the ranges above) AND BNG with PPPoE termination on Lightspeed/Lightspeed-Plus line cards is actively configured.

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 7.9.21 / 7.10.1 / 7.11.1 or later
Fixed in 7.9.217.10.17.11.1
Interim mitigation

Apply the Cisco software update for CVE-2024-20327 when available; until then, consider network segmentation to limit adjacent attacker access to affected interfaces.

Recommended fix High confidence

Upgrade to IOS XR 7.9.21 / 7.10.1 / 7.11.1 or later (recommended: latest available stable release in your version branch)

  1. 1. Identify the current IOS XR version by running 'show version' on the router
  2. 2. Identify the line card type (Lightspeed or Lightspeed-Plus) by running 'show controller fia' or 'show platform'
  3. 3. Verify BNG/PPPoE termination is enabled by checking for 'ppp' or 'pppoe' configurations in the running config
  4. 4. Schedule a maintenance window for the upgrade
  5. 5. Back up the current router configuration using 'admin save configuration' or 'copy running-config tftp://<server>/<file>'
  6. 6. Download the appropriate fixed IOS XR software version from Cisco (7.9.21 or higher, 7.10.1 or higher, or 7.11.1 or higher)
  7. 7. Install the new software package using 'install add source <tftp-server> <package-name>' followed by 'install activate' and 'install commit'
  8. 8. After reboot, verify the ppp_ma process is running using 'show process ppp_ma'
Caveat Cisco IOS XR minor version upgrades typically retain configuration compatibility; however, always review release notes for any migration caveats before upgrading

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

Fix this in Ios Xr Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,120
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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-2024-20327 in production — separate from our analysis above.

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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
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  • Version or environment caveats, and links to real fixes
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