CVE-2026-53425: Missing InResponseTo validation in Samly allows acceptance of unsolicited SAML responses
dropbox · samly
Affected: dropbox samly · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 13% of scored CVEs
DescriptionCVE.org
Insufficient Verification of Data Authenticity vulnerability in dropbox samly allows an attacker to establish an authenticated session using a SAML response the service provider never requested. Samly.SPHandler.validate_authresp/3 in lib/samly/sp_handler.ex validates a SAML response for the SP-initiated flow by comparing only the RelayState value, the IdP identifier, and the presence of a target URL held in the session. It never compares SubjectConfirmationData/@InResponseTo against the ID of the AuthnRequest the service provider issued, and that request ID is never persisted, so no comparison is possible. SAML 2.0 Core section 4.1.4.3 requires a service provider to reject a response whose InResponseTo does not match a request it made. The underlying esaml library checks status, signature, recipient, audience, and staleness, but likewise never inspects InResponseTo, so nothing else closes the gap. Exploitation requires a validly signed assertion from the trusted IdP, which an attacker can obtain for their own account, and a RelayState matching the victim's session; the assertion signature itself remains intact, so this is not a signature-forgery issue. This issue affects samly: from 0.3.0 onward.
Affected products3
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- dropbox · samly0.3.0
- dropbox · samlyVersions not stated
- handnot2 · samlyVersions not stated
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- dropbox
- Published
- August 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-53425 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.