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Actively exploited

CVE-2023-29552 Service Location Protocol (SLP) Denial-of-Service Vulnerability

The Service Location Protocol (SLP) contains a denial-of-service (DoS) vulnerability that could allow an unauthenticated, remote attacker to register services and use spoofed UDP traffic to conduct a denial-of-service (DoS) attack with a significant amplification factor.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 8 Nov 2023.
  • Rated High severity (CVSS 7.5, scored by CISA).
  • It has been in the catalogue for 1,094 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

The Service Location Protocol (SLP, RFC 2608) allows an unauthenticated, remote attacker to register arbitrary services. This could allow the attacker to use spoofed UDP traffic to conduct a denial-of-service attack with a significant amplification factor.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for IETF Service Location Protocol (SLP). Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply mitigations per vendor instructions or disable SLP service or port 427/UDP on all systems running on untrusted networks, including those directly connected to the Internet.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 29 Nov 2023 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

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CVE-2023-44487HTTP/2 Rapid Reset Attack VulnerabilityAdded 10 Oct 2023

All 2 exploited IETF vulnerabilities

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2023-29552
  3. CVE record: CVE-2023-29552
  4. FIRST EPSS
  5. datatracker.ietf.org/doc/html/rfc2608
  6. bitsight.com/blog/new-high-severity-vulnerability-cve-2023-29552-discovered-service-location-protoco
  7. blogs.vmware.com/security/2023/04/vmware-response-to-cve-2023-29552-reflective-denial-of-service-dos
  8. cisa.gov/news-events/alerts/2023/04/25/abuse-service-location-protocol-may-lead-dos-attacks
  9. suse.com/support/kb/doc/?id=000021051
  10. curesec.com/blog/article/CVE-2023-29552-Service-Location-Protocol-Denial-of-Service-Amplification-At
  11. github.com/curesec/slpload
  12. security.netapp.com/advisory/ntap-20230426-0001/