Missing decompression size limit in agent receiver allows memory exhaustion via push agent data (CVE-2026-77021) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-77021

Missing decompression size limit in agent receiver allows memory exhaustion via push agent data

Answer in brief

CVE-2026-77021 records a Unknown severity vulnerability in Missing decompression size limit in agent receiver allows memory exhaustion via push agent data. The current sources do not mark it as known exploited. The current feed maps Checkmk GmbH/Checkmk (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 21, 2026Updated Sep 21, 2026Source checked Sep 21, 2026First seen by HOL Sep 21, 2026Material review Sep 21, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Checkmk GmbH/Checkmk (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Checkmk GmbH/Checkmkgeneric	>=2.5.0 <2.5.0p14 \|\| >=2.4.0 <2.4.0p37 \|\| >=2.3.0 <2.3.0p51 \|\| 2.2.0	2.5.0p14, 2.4.0p37, 2.3.0p51

Recommended response

Check inventory. Check lockfiles and deployed manifests for Checkmk GmbH/Checkmk.
Review the reported fix. Update Checkmk GmbH/Checkmk to 2.5.0p14 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 21, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 21, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 21, 2026

Sources and claim methodology

Source referencecheckmk.com

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.