Detect CVE-2026-33646: Mise Arbitrary Code Execution via Tera Template Injection in .tool-versions in Splunk
Detects exploitation of CVE-2026-33646, a critical trust bypass vulnerability in mise (formerly rtx) versions prior to 2026.3.10. Attackers can embed Tera template directives inside .tool-versions files to achieve arbitrary code execution when mise processes the file, bypassing trust checks. CVSS 9.6. PoC public.
MITRE ATT&CK
- Tactic
- Execution Persistence Defense Evasion
SPL Detection Query
index=endpoint sourcetype IN ("XmlWinEventLog:Microsoft-Windows-Sysmon/Operational", "linux_secure", "osquery")
(EventCode=11 OR EventCode=1 OR event_type IN ("file_write", "process"))
| eval file_lower=lower(TargetFilename)
| eval proc_lower=lower(Image)
| where (match(file_lower, "\.tool-versions$") AND match(CommandLine, "\{%|\{\{|\{#"))
OR (match(proc_lower, "(^|/)mise(\.exe)?$") AND match(CommandLine, "install|trust|run|exec|shell"))
| eval event_type=case(
match(file_lower, "\.tool-versions$"), "tool_versions_write",
match(proc_lower, "(^|/)mise(\.exe)?$"), "mise_execution",
true(), "unknown")
| stats values(CommandLine) as commands, values(event_type) as event_types, count by host, user, _time
| where mvcount(event_types) > 1 OR (mvcount(event_types)==1 AND mvfind(event_types, "tool_versions_write") >= 0)
| eval risk_score=90
| table _time, host, user, commands, event_types, risk_scoreDetects .tool-versions file writes containing Tera template syntax followed by mise execution on the same host, using Sysmon or osquery telemetry.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Legitimate developer workflows writing complex .tool-versions configurations
- Automated provisioning scripts that generate .tool-versions and call mise in sequence
- CI/CD pipeline agents running mise commands on freshly cloned repositories
Other platforms for CVE-2026-33646
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Inject Tera system() call into .tool-versions and invoke mise install
Expected signal: File write event for .tool-versions, followed by mise process launch, followed by child process executing 'id' or shell writing to /tmp/mise-pwned.txt
- Test 2Malicious .tool-versions via Git Clone Simulation
Expected signal: Directory creation, .tool-versions file write by shell (not interactive mise), then mise process launch with install argument
- Test 3mise trust bypass via template in project-local .tool-versions
Expected signal: osascript child process spawned from mise with suspicious arguments, .tool-versions read by mise process
- Test 4Enumerate environment variables via Tera template injection
Expected signal: File write of .tool-versions, mise process launch, child write to /tmp/mise-env-leak.txt containing environment variable value
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