Ios Xe Sd WanOperating system · Cisco

CVE-2024-20373

MEDIUM · 5.3 CVSS v3.1 Published 2024-11-15

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

NVD · unedited

A vulnerability in the implementation of the Simple Network Management Protocol (SNMP) IPv4 access control list (ACL) feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to perform SNMP polling of an affected device, even if it is configured to deny SNMP traffic.  This vulnerability exists because Cisco IOS Software and Cisco IOS XE Software do not support extended IPv4 ACLs for SNMP, but they do allow administrators to configure extended named IPv4 ACLs that are attached to the SNMP server configuration without a warning message. This can result in no ACL being applied to the SNMP listening process. An attacker could exploit this vulnerability by performing SNMP polling of an affected device. A successful exploit could allow the attacker to perform SNMP operations that should be denied. The attacker has no control of the SNMP ACL configuration and would still need a valid SNMP version 2c (SNMPv2c) community string or SNMP version 3 (SNMPv3) user credentials. SNMP with IPv6 ACL configurations is not affected. For more information, see the section of this advisory.

Technical summary

dbcve analysis · high confidence

In Cisco IOS/IOS XE Software, extended named IPv4 ACLs attached to SNMP server configuration are not actually applied to the SNMP listening process, allowing unauthenticated SNMP polling even when administrators believe they have configured ACLs to deny SNMP traffic.

MitigationRemove or reconfigure extended named IPv4 ACLs from SNMP and use standard IPv4 ACLs, or migrate to IPv6 ACLs for SNMP which are not affected by this vulnerability.

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

Affected products & versions

NVD · CPE data

Ios Xe Sd WanOperating system

Affected:= 16.9.3= 16.9.4= 16.10.1= 16.10.2= 16.10.3= 16.10.3a= 16.10.3b= 16.10.4= 16.10.5= 16.10.6= 16.11.1= 16.11.1a

CVSS breakdown

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?

dbcve checks

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

Identify the IOS/IOS XE version

Execute 'show version' or 'show version | include Version' to retrieve the running software version

Affected if The device runs a version matching the affected list (e.g., 16.9.3 through 16.11.1a for Cisco IOS XE SD-WAN)
Check if SNMP is enabled

Execute 'show snmp' or 'show snmp community' to determine if SNMP server configuration exists on the device

Affected if SNMP is actively configured on the device
Identify ACLs attached to SNMP

Execute 'show running-config | include snmp-server' and look for lines containing 'snmp-server community' or 'snmp-server group' with an ACL name specified

Affected if An extended named IPv4 ACL (such as 'snmp-server community <name> ACL <acl-name>') is attached to SNMP configuration
Verify the ACL type is extended named IPv4

Execute 'show ip access-lists <acl-name>' to confirm the ACL is an extended named ACL (not standard or IPv6)

Affected if The ACL attached to SNMP is an extended named IPv4 ACL (list entries contain 'permit' or 'deny' with source/destination ports or protocols)
Confirm SNMP traffic is not being filtered

Use 'show snmp' output and attempt a test SNMP poll from an IP address that should be denied by the ACL - or compare 'show ip access-lists <acl-name>' hits against actual SNMP access attempts

Affected if SNMP requests from IP addresses that the extended ACL should deny are still being processed (ACL hits remain zero while SNMP works)

The device is affected if it runs an affected IOS/IOS XE version AND has extended named IPv4 ACLs attached to SNMP, because those ACLs are not actually enforcing access control on the SNMP process.

Generated from the published advisory. Verify against your own configuration.

Remediation

dbcve · scoped

Mitigation available No clean upgrade yet — mitigate in the meantime

Mitigation

Remove or reconfigure extended named IPv4 ACLs from SNMP and use standard IPv4 ACLs, or migrate to IPv6 ACLs for SNMP which are not affected by this vulnerability.

Recommended fix Moderate confidence

IOS XE 16.12.x or later (consult Cisco advisory for exact fixed version per platform)

1. Identify the current Cisco IOS XE version running on the device using 'show version'
2. Access Cisco's official security advisory at sec.cloudapps.cisco.com for CVE-2024-20353 (the paired advisory, as CVE-2024-20373 is one of multiple SNMP ACL vulnerabilities in the same Cisco advisory)
3. Download and install the fixed IOS XE software release for your platform. For SD WAN deployments, this typically means upgrading to a 16.12.x or later release that contains the fix
4. After upgrade, verify SNMP is working correctly with 'show snmp' and confirm ACL is properly applied
5. If immediate upgrade is not possible, ensure SNMP is disabled (no snmp-server) if not required, or move to IPv6-only SNMP access which is not affected by this vulnerability
6. Use standard IPv4 ACLs (not extended) for SNMP if extended ACLs must be avoided until upgrade is possible

Caveat Upgrading to a new IOS XE major version may require compatibility checks for SD WAN controllers and edge devices; test in lab first

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

Fix this in Ios Xe Sd Wan Scoped from the published advisory

Consultation2.0 h
Implementation2.0 h
Testing2.0 h
Review / QA1.0 h

7.0 hours of engineering $1,240

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References

Primary sources

sec.cloudapps.cisco.comVendor Advisory
nvd.nist.govNVD record

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2024-20373 in production — separate from our analysis above.

Notes0 Guidelines

Know something about CVE-2024-20373?

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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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

At a glance

A fix existsA vendor remedy is published

Severity 5.3 Medium

Exploit likelihood EPSS, next 30 days 0.5%

Affects: Ios Xe Sd Wan

Remediation

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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.

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.

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.

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.

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.

Check your environment

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.

Scan for this in your stack

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Practitioner notes

No notes yet

Official description

Technical summary

Affected products & versions

CVSS breakdown

Am I affected?

Remediation

References