# CVE-2026-53425: Dropbox Samly SAML authentication bypass

Source: https://junglewise.ai/threats/cve-2026-53425-dropbox-samly-saml-authentication-bypass  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-20. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-53425 · Severity: info · Published 2026-08-20

Samly is a library used to integrate SAML single sign-on authentication into applications. A vulnerability in its SAML response validation allows an attacker to hijack a victim's authenticated session by replaying a SAML response from the trusted identity provider without verifying the response matches a specific login request. This could allow unauthorized access to accounts without knowing passwords.

## Quick answers

**Is CVE-2026-53425 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-53425 being exploited in the wild.

**How severe is CVE-2026-53425?** Informational severity, published 20 August 2026.

**Which products and versions are affected?** Dropbox Samly 0.3.0 and later.

**Is there a fix for CVE-2026-53425?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-53425 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-53425?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an insufficient verification of data authenticity in Samly's SPHandler.validate_authresp/3 function. The code validates SAML responses by checking RelayState, IdP identifier, and session target URL, but fails to verify that the SubjectConfirmationData/@InResponseTo attribute matches the ID of the AuthnRequest originally issued by the service provider. SAML 2.0 Core section 4.1.4.3 mandates this check to prevent response replay attacks. Exploitation requires a validly signed SAML assertion from the trusted IdP (obtainable using the attacker's own account) and knowledge of a victim's RelayState session value. The underlying esaml library also does not verify InResponseTo, closing no alternative validation path. No patch information is currently available.

## Affected products

- Dropbox Samly 0.3.0 and later

## Timeline

- 2026-08-20: disclosed

## References

- [https://repo.hex.pm/](https://repo.hex.pm/)
- [https://github.com/](https://github.com/)