High severity · published Sep 27, 2026
CVE-2026-100864
heym before 0.0.91 Remote Code Execution via Expression Engine
8.8
CVSS
0.9%
EPSS
No
On KEV
Description
heym before 0.0.91 contains a sandbox escape vulnerability in the expression engine's DotList map/filter and fallback resolver that allows authenticated users to execute arbitrary Python code. Attackers can craft workflow expressions using dunder attribute access through item expressions or the fallback resolver to access os.system and execute commands as the backend process.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.9% · higher than 58% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
HE
heym · heymrun
before 0.0.91 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-100864
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-100864
vendor-advisory
https://github.com/heymrun/heym/security/advisories/GHSA-87x2-9jwx-7gh4
third-party-advisory
https://www.vulncheck.com/advisories/heym-before-0.0.91-remote-code-execution-via-expression-engine
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