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CVE-2026-49283— SimpleSAMLphp HTTP-Artifact TLS validator confusion allows cross-IdP authentication bypass

Quick assessment

Affected
simplesamlphp saml2
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

SimpleSAMLphp saml2是SimpleSAMLphp组织开源的一个身份认证协议实现库。 SimpleSAMLphp saml2 4.19.3之前版本、4.20.2之前版本、5.0.6之前版本和6.2.1之前版本存在加密问题漏洞，该漏洞源于HTTPArtifact::receive()流程可能将未签名的嵌入式SAML响应视为对错误身份提供方有效，导致恶意或低信任身份提供商可以冒充任意用户进行身份验证。

CVSS 8.7 · High EPSS 0.34% · P28

Possible ATT&CK Techniques 1 AI

T1199 · Trusted Relationship

Affected Version Matrix 4

VendorProduct Version RangeStatus
simplesamlphp saml2 < 4.19.3 affected
>= 4.20.0, < 4.20.2 affected
>= 5.0.0, < 5.0.6 affected
>= 6.0.0, < 6.2.1 affected
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I. Basic Information for CVE-2026-49283

Vulnerability Information
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Vulnerability Title
SimpleSAMLphp HTTP-Artifact TLS validator confusion allows cross-IdP authentication bypass
Source: CVE Program / CVE List V5
Vulnerability Description
The SimpleSAMLphp SAML2 library is a PHP library for SAML2 related functionality. Prior to versions 4.19.3, 4.20.2, 5.0.6, and 6.2.1, the HTTPArtifact::receive() flow can treat an unsigned embedded SAML Response as cryptographically valid for the wrong identity provider. SOAPClient::addSSLValidator() attaches a TLS-based validator to the outer SOAP ArtifactResponse, while the embedded Response receives a validator that delegates to the outer message and is later checked against metadata selected from the embedded response issuer rather than necessarily the artifact issuer. SOAPClient::validateSSL() returns normally when the TLS public key does not match the key being validated, and SAML2\Message::validate() treats a validator call that does not throw as successful. In a multi-IdP federation, a malicious or lower-trust IdP can therefore provide an ArtifactResponse containing an unsigned Response that claims a higher-trust victim IdP as issuer and authenticate as arbitrary users with attacker-chosen assertion attributes, NameID, and session data. This issue is fixed in versions 4.19.3, 4.20.2, 5.0.6, and 6.2.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
证书验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
SimpleSAMLphp saml2 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
SimpleSAMLphp saml2是SimpleSAMLphp组织开源的一个身份认证协议实现库。 SimpleSAMLphp saml2 4.19.3之前版本、4.20.2之前版本、5.0.6之前版本和6.2.1之前版本存在加密问题漏洞，该漏洞源于HTTPArtifact::receive()流程可能将未签名的嵌入式SAML响应视为对错误身份提供方有效，导致恶意或低信任身份提供商可以冒充任意用户进行身份验证。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
simplesamlphp saml2 < 4.19.3 -

II. Public POCs for CVE-2026-49283

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-49283

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Patches & Fixes for CVE-2026-49283 (3)

Vendor Advisories for CVE-2026-49283 (1)

IV. Related Vulnerabilities

Same product: saml2
Same vendor: simplesamlphp
Same weakness: CWE-295

V. Comments for CVE-2026-49283

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