CVE-2026-77021 Details
Description
Improper handling of highly compressed data (data amplification) in Checkmk <2.5.0p14, <2.4.0p37, <2.3.0p51 and 2.2.0 (EOL) allows an attacker who controls a host registered for push mode to exhaust the memory of the agent receiver by sending a small zlib compressed payload that decompresses to an arbitrary size.
A vulnerability exists in Checkmk versions prior to 2.5.0p14, 2.4.0p37, 2.3.0p51, and 2.2.0 (EOL). It allows an attacker controlling a host registered for push mode to send a small zlib-compressed payload that decompresses to an arbitrary size. This improper handling of highly compressed data can lead to memory exhaustion on the agent receiver.
Users can update to Checkmk versions 2.5.0p14, 2.4.0p37, or 2.3.0p51. The updated agent receiver now rejects data whose decompressed size exceeds 512 MiB, responding with 'Decompression of agent data failed'. No reconfiguration is required after updating.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 21, 2026CISA-ADP
Assessed Sep 21, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://checkmk.com/werk/22116 | [email protected] | AdvisoryRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-409 | Improper Handling of Highly Compressed Data (Data Amplification) | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Checkmk | < 2.5.0p14 < 2.4.0p37 < 2.3.0p51 2.2.0 (semver) |
CPE
Remediation
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| Checkmk Ultimate | All versions |
CPE
Remediation
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| Checkmk Cloud | All versions |
CPE
Remediation
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| Checkmk Ultimate MT | All versions |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 21, 2026 | CVE Modified | CISA-ADP |
| Sep 21, 2026 | New CVE Received | [email protected] |