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Unified Threat Defense Snort Intrusion Prevention System EngineOperating system · Cisco

CVE-2024-20508

MEDIUM · 6.5 CVSS v3.1 Published 2024-09-25
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
74/100
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 Cisco Unified Threat Defense (UTD) Snort Intrusion Prevention System (IPS) Engine for Cisco IOS XE Software could allow an unauthenticated, remote attacker to bypass configured security policies or cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient validation of HTTP requests when they are processed by Cisco UTD Snort IPS Engine. An attacker could exploit this vulnerability by sending a crafted HTTP request through an affected device. A successful exploit could allow the attacker to trigger a reload of the Snort process. If the action in case of Cisco UTD Snort IPS Engine failure is set to the default, fail-open, successful exploitation of this vulnerability could allow the attacker to bypass configured security policies. If the action in case of Cisco UTD Snort IPS Engine failure is set to fail-close, successful exploitation of this vulnerability could cause traffic that is configured to be inspected by Cisco UTD Snort IPS Engine to be dropped.

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 confidence

This vulnerability in Cisco UTD Snort IPS Engine for IOS XE allows an unauthenticated remote attacker to bypass security policies or cause DoS by sending specially crafted HTTP requests. The insufficient validation of HTTP requests triggers a Snort process reload. In default fail-open mode, this allows security policy bypass; in fail-close mode, legitimate traffic gets dropped.

MitigationApply the Cisco security update for CVE-2024-20508 when released. As an interim measure, verify the current fail-open/fail-close configuration and consider setting to fail-close to minimize policy bypass impact while awaiting the patch.

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
Unified Threat Defense Snort Intrusion Prevention System EngineOperating system
Affected:= 17.6.1a= 17.6.2= 17.6.6= 17.7.1a= 17.7.2= 17.8.1a= 17.9.5a= 17.11.1a= 17.12.1a= 17.12.2= 17.12.3= 17.12.3a

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
Low

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

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

  1. Confirm UTD Snort IPS Engine is running
    Execute 'show utd engine ips status' or 'show utd status' in IOS XE CLI to verify the Snort IPS engine is active
    Affected if If the command shows no UTD or Snort IPS engine is running, this CVE does not apply
  2. Identify installed Snort IPS Engine version
    Execute 'show utd engine ips version' or 'show version | include UTD' to retrieve the exact Snort IPS Engine version number
    Affected if If the version matches any of the following: 17.6.1a, 17.6.2, 17.6.6, 17.7.1a, 17.7.2, 17.8.1a, 17.9.5a, 17.11.1a, 17.12.1a, 17.12.2, 17.12.3, or 17.12.3a, the environment is vulnerable
  3. Check fail-open or fail-close configuration mode
    Execute 'show utd engine ips configuration' or 'show running-config | include fail-open' to see whether fail-open or fail-close mode is configured
    Affected if If fail-open mode is configured, an attacker can bypass security policies; if fail-close mode is configured, the DoS condition will cause legitimate traffic to be dropped

You are affected if the UTD Snort IPS Engine is running and its version matches one of the affected versions listed (17.6.x through 17.12.3a), regardless of the fail-open/fail-close setting, as both modes result in negative security impact from this vulnerability.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the Cisco security update for CVE-2024-20508 when released. As an interim measure, verify the current fail-open/fail-close configuration and consider setting to fail-close to minimize policy bypass impact while awaiting the patch.

Recommended fix Moderate confidence

Obtain the fixed Cisco IOS XE release from Cisco security advisory; the fixed version supersedes 17.7.1a

  1. 1. Identify the current Cisco IOS XE software version running on the affected device using 'show version' command.
  2. 2. Access Cisco's official security advisory portal at sec.cloudapps.cisco.com to obtain the specific fixed release for CVE-2024-20508.
  3. 3. Plan an upgrade window as the device will need to be reloaded to apply the new software image.
  4. 4. Download the fixed Cisco IOS XE software image containing the updated UTD Snort IPS Engine from Cisco's software download center.
  5. 5. Upload the new software image to the device using TFTP, FTP, or SCP.
  6. 6. Verify the software image integrity using the 'verify' command with the MD5/SHA256 hash provided by Cisco.
  7. 7. Configure boot system command to point to the new image: 'boot system <flash:|http:> <filename>'.
  8. 8. Save configuration with 'write memory' or 'copy running-config startup-config'.
Caveat Review Cisco IOS XE release notes for any changes to UTD functionality or configuration syntax before upgrading; some features may behave differently in newer major releases

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

Fix this in Unified Threat Defense Snort Intrusion Prevention System Engine Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA3.0 h
27.0 hours of engineering $4,800
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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-2024-20508 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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