Memory exhaustion via unlimited push-data decompression
Published Sep 21, 2026 · Updated Sep 21, 2026
Data amplification in Checkmk before 2.5.0p14, 2.4.0p37, or 2.3.0p51 allows remote authenticated users to exhaust receiver memory. The agent receiver decompresses zlib-compressed push agent data without limiting the resulting size, so a small payload expands to consume arbitrary memory. Exploitation requires control of a push-mode host and its registered client certificate; exhausting memory interrupts the receiver service.
Summary
What happened
Data amplification in Checkmk before 2.5.0p14, 2.4.0p37, or 2.3.0p51 allows remote authenticated users to exhaust receiver memory. The agent receiver decompresses zlib-compressed push agent data without limiting the resulting size, so a small payload expands to consume arbitrary memory. Exploitation requires control of a push-mode host and its registered client certificate; exhausting memory interrupts the receiver service.
The record
- CVE
- CVE-2026-77021
- Published
- Sep 21, 2026
- Updated
- Sep 21, 2026
- Vendor
- Checkmk GmbH
- Product
- Checkmk
- Classifications
- CWE-409, T1499.004
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 21, 2026CVE publishedPublication date reported by the CVE source.
- Sep 21, 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=2.2.0
- Affected versionversion=2.3.0 <2.3.0p51
- Affected versionversion=2.4.0 <2.4.0p37
- Affected versionversion=2.5.0 <2.5.0p14
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
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.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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