What is CVE-2026-105396?

CVE-2026-105396 is a medium-severity vulnerability in Heymrun Heym, classified under Origin Validation Error. CVSS score: 5.4/10. Published 2026-10-05.

How severe is CVE-2026-105396?

Medium severity. CVSS v3 base score is 5.4 out of 10.

Vulnerability in Heymrun Heym

CVE-2026-105396

Heym before v0.0.112 contains a token leakage vulnerability in build_public_base_url() that allows unauthenticated attackers to redirect HITL review links by spoofing Origin or X-Forwarded-Host headers. Attackers can trigger anonymous workflows with forged headers so reviewer notifications point to attacker domains, capturing capability tokens to submit decisions executed with owner credentials.

Published 2026-10-05 · last modified 2026-10-05.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Heymrun Heym

Weakness classification (CWE)

CWE-346 — Origin Validation Error

References

github.com/heymrun/heym/security/advisories/GHSA-6rv3-wh25-7pg5 (vendor-advisory)
www.vulncheck.com/advisories/heym-before-0.0.112-hitl-review-token-leak-via-spo… (third-party-advisory)

Frequently asked questions

What is CVE-2026-105396?: CVE-2026-105396 is a medium-severity vulnerability in Heymrun Heym, classified under Origin Validation Error. CVSS score: 5.4/10. Published 2026-10-05.
How severe is CVE-2026-105396?: Medium severity. CVSS v3 base score is 5.4 out of 10.