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Improper Access ControlWeakness · CWE-284

CVE-2025-20159

MEDIUM · 5.3 CVSS v3.1 Published 2025-09-10
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
62/100
Remediation priority · Elevated
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 management interface access control list (ACL) processing feature in Cisco IOS XR Software could allow an unauthenticated, remote attacker to bypass configured ACLs for the SSH, NetConf, and gRPC features. This vulnerability exists because management interface ACLs have not been supported on Cisco IOS XR Software Packet I/O infrastructure platforms for Linux-handled features such as SSH, NetConf, or gRPC. An attacker could exploit this vulnerability by attempting to send traffic to an affected device. A successful exploit could allow the attacker to bypass an ingress ACL that is applied on the management interface of the affected device.

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

In Cisco IOS XR Software on Packet I/O infrastructure platforms, management interface ACLs designed to filter SSH, NetConf, and gRPC traffic are not enforced because these services run on Linux and bypass the traditional ACL processing path. An attacker sending traffic to the management interface can bypass configured ACLs entirely, gaining unauthorized access to these management services despite ACLs being apparently applied.

MitigationConfigure ACLs using the control plane policing (CoPP) feature or platform-specific ACL mechanisms supported by the device, or apply Cisco-provided fixes/upgrades that enable proper ACL enforcement for Linux-handled management services.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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
Low
Availability
None

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

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 platform type and IOS XR version
    Run 'show version' or 'cat /proc/version' to confirm the device runs Cisco IOS XR Software on Packet I/O infrastructure platforms. Note the full software version string.
    Affected if The device runs IOS XR on Packet I/O infrastructure and the version is within the affected range (if known) or unpatched.
  2. Verify management interface ACL configuration
    Run 'show running-config interface mgmtEth 0/RP0/CPU0/0' (or relevant management interface) and look for 'access-group' or 'ipv4 access-list' / 'ipv6 access-list' applied to the interface.
    Affected if An ACL is applied to the management interface (e.g., 'ip access-group' or 'ipv6 access-group' is present in the config).
  3. Confirm vulnerable services enabled on management interface
    Run 'show ssh' and check configuration for NetConf (show netconf-yang) and gRPC (show grpc) status. Verify these services are enabled and bound to the management interface.
    Affected if SSH, NetConf, or gRPC services are enabled and accessible via the management interface.
  4. Check if CoPP mitigation is configured
    Run 'show running-config | include copp' or 'show control-plane' to see if Control Plane Policing is configured to filter management traffic.
    Affected if CoPP is NOT configured - the device relies solely on management interface ACLs which are bypassed.
  5. Test ACL enforcement effectiveness
    From an external host, attempt to reach the management interface IP on ports 22 (SSH), 830 (NetConf), or 57400 (gRPC) from an IP address that should be blocked by the configured management ACL.
    Affected if Traffic from a blocked source IP successfully connects to SSH, NetConf, or gRPC on the management interface despite ACL configuration.

A user is affected if the device runs Cisco IOS XR on Packet I/O infrastructure, has management interface ACLs configured, and has SSH/NetConf/gRPC services enabled - because such ACLs are bypassed for Linux-hosted management services.

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

Configure ACLs using the control plane policing (CoPP) feature or platform-specific ACL mechanisms supported by the device, or apply Cisco-provided fixes/upgrades that enable proper ACL enforcement for Linux-handled management services.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2025-20159 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
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