Missing decompression size limit in agent receiver allows memory exhaustion via push agent data
Priority LOW 24CWE-409Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · Low
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
Summary
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.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00382 32nd percentileScored 2026-11-07
Fix Fixed Checkmk (Checkmk GmbH): 2.5.0p14, 2.4.0p37, 2.3.0p51
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Checkmk GmbH | Checkmk | 2.5.0 to before 2.5.0p14; 2.4.0 to before 2.4.0p37; 2.3.0 to before 2.3.0p51; 2.2.0 | 2.5.0p14, 2.4.0p37, 2.3.0p51 | Patch available | CNA |
- Checkmk VendorCheckmk GmbH Affected 2.5.0 to before 2.5.0p14; 2.4.0 to before 2.4.0p37; 2.3.0 to before 2.3.0p51; 2.2.0 Fixed in 2.5.0p14, 2.4.0p37, 2.3.0p51 Patch available CNA
CPE names Threatist (inferred) · 1
Inferred from how NVD named this product before; not given by a source.
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:checkmk:checkmk:*:*:*:*:*:*:*:* | — | — | Checkmk GmbH |
- cpe:2.3:a:checkmk:checkmk:*:*:*:*:*:*:*:* Versions — — ·Checkmk GmbH
Remediation
- Fix · CNA Checkmk (Checkmk GmbH) Fixed in 2.5.0p14, 2.4.0p37, 2.3.0p51
Timeline
- 2026-10-02 Threatist record created from CVE-2026-77021
- 2026-10-03 Alias added: GHSA-5q8h-fhcg-2395
References
Advisory 1
More Checkmk GmbH vulnerabilities
- TI-2025-26345 Cross Site Scripting through compromised remote site CVSS 4.0HIGH 8.5
- TI-2025-40190 Cross-site scripting in HTML logs of Synthetic Monitoring test services CVSS 4.0HIGH 7.3
- TI-2024-12762 Checkmk NagVis Remote Code Execution CVSS 3.1HIGH 7.2
- TI-2024-12761 Checkmk NagVis Reflected Cross-site Scripting CVSS 3.1MEDIUM 5.4
- TI-2024-19037 Brute-force protection ineffective for some login methods CVSS 3.1CRITICAL 9.8
- TI-2024-05712 local IP restriction of internal HTTP endpoints CVSS 3.1CRITICAL 9.8
Sources
- CVE-2026-77021 · CVE Program
- CVE-2026-77021 · NVD
- FIRST EPSS
- GHSA-5q8h-fhcg-2395 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences