CVE-2026-65840 (CVSS 9.6)

Description

Fider is a feedback portal for feature requests and suggestions. Prior to version 0.36.0, in multi-tenant mode (HOST_MODE=multi), an attacker can use an email verification key issued by Tenant A to authenticate as the same email address on Tenant B. This completely bypasses tenant isolation and allows unauthorized account takeover across tenants. Single-host deployments (HOST_MODE=single, the default) are NOT affected. This issue has been patched in version 0.36.0.

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CVSS v3.1 Score

9.6

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

EPSS — Exploit Prediction

0.0030

Probability of exploitation

0.23%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-639 CWE-639

References

Other References

https://github.com/getfider/fider/releases/tag/v0.36.0 https://github.com/getfider/fider/security/advisories/GHSA-vxjw-gv4f-vq58

Frequently Asked Questions

What is CVE-2026-65840? +

Fider is a feedback portal for feature requests and suggestions. Prior to version 0.36.0, in multi-tenant mode (HOST_MODE=multi), an attacker can use an email verification key issued by Tenant A to authenticate as the same email address on Tenant B. This completely bypasses tenant isolation and allows unauthorized account takeover across tenants. Single-host deployments (HOST_MODE=single, the default) are NOT affected. This issue has been patched in version 0.36.0. It has a CVSS v3.1 base score of 9.6 (CRITICAL).

How severe is CVE-2026-65840? +

CVE-2026-65840 has a CVSS v3.1 score of 9.6 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0030, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-65840? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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