CVE-2026-100864 json
heym before 0.0.91 Remote Code Execution via Expression Engine
published last mo. modified last mo. also EUVD-2026-87829
- cvss
- 8.8
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.9%
- EPSS 0.9% chance of exploitation in 30 days, percentile 58%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- heymrun heym 0.0.91
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Check with FencerCISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- no
- Technical impact
- total
- Assessed
- last mo.
Exploit prediction
0.86% chance of exploitation in the next 30 days, higher than 58% of all scored CVEs (FIRST EPSS, 2026-11-09).
Exploits and checks
- github.com https://github.com/heymrun/heym/security/advisories/GHSA-87x2-9jwx-7gh4 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 8.7 | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N |
| CNA | 3.1 | 8.8 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| CNA | 4.0 | 8.7 | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/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 |
Affected products
- heymrun heym
Classification
- Weakness
-
- CWE-94 Improper Control of Generation of Code
References
-
github.com
/heymrun/heym/security/advisories/GHSA-87x2-9jwx-7gh4
vendor-advisory, exploit
-
vulncheck.com
/advisories/heym-before-0.0.91-remote-code-execution-via-expression-engine
third-party-advisory
Sources
- CVE List CVE-2026-100864
- NVD CVE-2026-100864
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