Adjacent-network code execution via unchecked SLP message length
Published Feb 24, 2021 · Updated Jun 2, 2026
Heap-based buffer overflow in OpenSLP on affected VMware ESXi 6.5, 6.7, and 7.0 builds allows remote attackers to execute code. The SLP message parser copies user-supplied data into a heap buffer without first validating its length. Exploitation requires no authentication but requires access to port 427 from the same network segment, and successful execution runs in the SLP daemon context.
Summary
What happened
Heap-based buffer overflow in OpenSLP on affected VMware ESXi 6.5, 6.7, and 7.0 builds allows remote attackers to execute code. The SLP message parser copies user-supplied data into a heap buffer without first validating its length. Exploitation requires no authentication but requires access to port 427 from the same network segment, and successful execution runs in the SLP daemon context.
The record
- CVE
- CVE-2021-21974
- Published
- Feb 24, 2021
- Updated
- Jun 2, 2026
- Vendor
- VMware
- Product
- VMware Cloud Foundation
- Classifications
- CWE-787, T1210
- Attack vector
- adjacent
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 24, 2021CVE publishedPublication date reported by the CVE source.
- Jun 2, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=4.x before 4.2 and 3.x
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- VMware ESXi OpenSLP Heap Overflow PoCfunctional · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- ESXiArgs ransomware exploitation reportsransomware
Technologies
Your stack
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Your stack
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