Missing one-time-use enforcement in Samly allows replay of SAML bearer assertions (CVE-2026-53424) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-53424

Missing one-time-use enforcement in Samly allows replay of SAML bearer assertions

Answer in brief

CVE-2026-53424 records a Unknown severity vulnerability in Missing one-time-use enforcement in Samly allows replay of SAML bearer assertions. The current sources do not mark it as known exploited. The current feed maps dropbox/samly (generic), dropbox/samly (generic), handnot2/samly (generic), dropbox/samly (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 20, 2026Updated Aug 20, 2026Source checked Aug 20, 2026First seen by HOL Aug 20, 2026Material review Aug 20, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 4 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps dropbox/samly (generic), dropbox/samly (generic), handnot2/samly (generic), dropbox/samly (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
dropbox/samlygeneric	>=v0.3.0 <*	*
dropbox/samlygeneric	>=8a5bb1b4a4753d05470da2036323477f63cfdf4c <*	*
handnot2/samlygeneric	>=8a5bb1b4a4753d05470da2036323477f63cfdf4c <*	*
dropbox/samlygeneric	>=0.3.0 <*	*

Recommended response

Check inventory. Check lockfiles and deployed manifests for dropbox/samly, dropbox/samly, handnot2/samly.
Review the reported fix. Update dropbox/samly to *; dropbox/samly to *; handnot2/samly to *; dropbox/samly to * if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 20, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 20, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 20, 2026

Sources and claim methodology

Upstream source description

Authentication Bypass by Capture-replay vulnerability in dropbox samly allows an attacker to authenticate as the subject of a captured SAML assertion by resubmitting it. Samly.Helper.decode_idp_auth_resp/3 in lib/samly/helper.ex calls esaml_sp:validate_assertion/2, whose default duplicate detector is a no-op. The /3 arity accepting a DuplicateFun exists in esaml and implements the check, but Samly never calls it and offers no configuration to supply one, so the SAML 2.0 Web Browser SSO Profile requirement that a bearer assertion be used once is unenforced. An attacker holding a valid SAMLResponse obtained from the network, from browser history, or from logs can submit the identical bytes repeatedly until the assertion's NotOnOrAfter passes, each time establishing a session as the assertion's subject. This issue affects samly: from 0.3.0 onward.

Quoted source text, attributed separately from HOL analysis.