EEF-CVE-2026-53424 CVE-2026-53424
Missing one-time-use enforcement in Samly allows replay of SAML bearer assertions
- Severity
- 0.0 / 10
- Unknown · CVSS 4.0
- Exploit chance (EPSS)
- 0.60%
- Chance of exploitation in the next 30 days. Higher than 48.82% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-294 Authentication Bypass by Capture-replay
- Fix
- None yet
- No fixed version published
Description
Summary
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.
Affected versions
Hex
| Package | Vulnerable | Fixed in |
|---|---|---|
| samly | >= 0.3.0 |
No fix yet |
How to fix
No fixed version has been published yet. Until one is, remove or replace the package, or turn off or isolate the affected feature. This page updates when a fix ships.
Severity breakdown
CVSS 4.0 0.0
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- Present
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- High
- Integrity (vulnerable system)
- High
- Availability (vulnerable system)
- None
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
Weakness
CWE-294: Authentication Bypass by Capture-replay
A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes).
How to prevent it
- Architecture and Design: Utilize some sequence or time stamping functionality along with a checksum which takes this into account in order to ensure that messages can be parsed only once.
- Architecture and Design: Since any attacker who can listen to traffic can see sequence numbers, it is necessary to sign messages with some kind of cryptography to ensure that sequence numbers are not simply doctored along with content.
References
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| EEF-CVE-2026-53425 Missing InResponseTo validation in Samly allows acceptance of unsolicited SAML responses | Not rated yet | Also affects samly |
| GHSA-h3rw-77w7-92gf Samly access control vulnerability | Critical | Also affects Samly |
| EEF-CVE-2026-87119 mpp Tempo subscription key authorization is not bound to the issuing challenge, allowing a captured activation credential to be replayed | Not rated yet | Same weakness, CWE-294 |
| GHSA-9xv2-5v5q-p794 Apache Tomcat's DIGEST authenticator has an Authentication Bypass by Capture-replay vulnerability | Critical | Same weakness, CWE-294 |
| EEF-CVE-2026-67581 On-chain transfer proof is not single-use in mpp EVM payment method, enabling cross-challenge replay | High | Same weakness, CWE-294 |
| EEF-CVE-2026-73136 Static memo configuration in mpp Tempo disables per-challenge attribution binding, enabling third-party replay | High | Same weakness, CWE-294 |
| GHSA-wg23-69c2-gjc8 Craft CMS: Passkey login accepts replayed WebAuthn assertions | Medium | Same weakness, CWE-294 |
| EEF-CVE-2026-53431 Boruta accepts expired JWT client assertions due to missing exp claim validation | Not rated yet | Same weakness, CWE-294 |
Credits: Jonatan Männchen / EEF, Mark Madsen
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