CVE-2025-64998: Exposure of session signing secret in Checkmk <2.4.0p23, <2.3.0p45 and 2.2.0 allows an administrator of a remo

Routine

HIGH 7.2DOWNGRADE

CVE-2025-64998 is a high-severity flaw (CVSS 7.2) affecting checkmk. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Exposure of session signing secret in Checkmk <2.4.0p23, <2.3.0p45 and 2.2.0 allows an administrator of a remote site with config sync enabled to hijack sessions on the central site by forging session cookies.

Why this priority

High severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.2 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	None
EPSS exploit chance	0.3% (top 72%)
CISA exploited list	No
Weakness	CWE-522
Published	2026-03-24
Last modified	2026-06-17

Publisher (CNA): Checkmk GmbH · Vendor: checkmk

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-24 12:16 UTCPublished CVE record published
2026-06-17 09:55 UTCUpdated Record last modified

checkmk checkmk DOWNGRADE

Affected: 2.2.0 · 2.2.0 b1 · 2.2.0 b2 · 2.2.0 b3 · 2.2.0 b4 · 2.2.0 b5 · 2.2.0 b6 · 2.2.0 b7

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.2.0

1. Check installed version

apt-cache policy checkmk || rpm -q checkmk || checkmk --version

2. No fixed release: DOWNGRADE to a release before 2.2.0 (Debian / Ubuntu)

apt-cache madison checkmk sudo apt install checkmk=<VERSION_BEFORE_2.2.0> sudo apt-mark hold checkmk

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list checkmk sudo dnf downgrade checkmk-<VERSION_BEFORE_2.2.0> sudo dnf versionlock add checkmk

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-64998?

checkmk: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2025-64998 being exploited?

CVE-2025-64998 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-64998 affect?

CVE-2025-64998 affects checkmk. Severity is high (CVSS 7.2). Exposure of session signing secret in Checkmk <2.4.0p23, <2.3.0p45 and 2.2.0 allows an administrator of a remote site with config sync enabled to hijack sessions on the central site by forging session cookies.

How urgent is CVE-2025-64998?

Priority 32/100. High severity

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References

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