Checkmk: Relative Path Traversal
CVE-2026-120495 is a critical-severity relative path traversal vulnerability in Checkmk, with a CVSS 4.0 base score of 9.4 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists versions 2.5.0p19, 2.4.0p40 as the first without the flaw, so updating Checkmk to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.46% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Checkmk to 2.5.0p19 or 2.4.0p40, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Checkmk | Checkmk | 2.5.0 up to, but not including, 2.5.0p19; 2.4.0 up to, but not including, 2.4.0p40; 2.3.0 | 2.5.0p19, 2.4.0p40 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Attack requirements
- NoneThe attack does not depend on a particular deployment or configuration.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Confidentiality (vulnerable system)
- HighSerious loss of confidentiality on the vulnerable system.
- Integrity (vulnerable system)
- HighSerious loss of integrity on the vulnerable system.
- Availability (vulnerable system)
- HighSerious loss of availability on the vulnerable system.
- Confidentiality (other systems)
- HighSerious loss of confidentiality on systems beyond the vulnerable one.
- Integrity (other systems)
- HighSerious loss of integrity on systems beyond the vulnerable one.
- Availability (other systems)
- HighSerious loss of availability on systems beyond the vulnerable one.
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. Scored by CNA (checkmk.com).
Official description
Path traversal in the Synthetic Monitoring "Robotmk" test service of Checkmk <2.5.0p19, <2.4.0p40, and 2.3.0 (EOL) allows an attacker who controls the agent output of a monitored host's check output for a host to inject a crafted robot output to define the contents and location for the generated HTML log, leading to code execution as the site user.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Relative Path Traversal
The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as.. that can resolve to a location that is outside of that directory.
How developers prevent this class of flaw
- Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in Checkmk
- 9.4 Critical severity
- 9.4 Critical severity
- 7.1 High severity
- 8.6 High severity
- 7.8 High severity
- 7.6 High severity
Recent Relative Path Traversal vulnerabilities
- 8.5 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 9.8 Critical severity
- 7.3 High severity
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