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CVE-2026-63182— LightSAML: Signature reference wrapping permits unsigned assertion claims

Quick assessment

Affected
litesaml lightsaml
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

LightSAML 实现了 SAML 2.0 数据模型类、XML 序列化与反序列化、XML 安全、证书支持以及消息绑定功能。在 4.7.1 和 5.0.1 版本之前，LightSAML 与 xmlseclibs 对于“入站 SAML 签名究竟覆盖哪条断言（Assertion）”存在理解分歧。 具体而言， 方法使用 仅收集 的直接子元素 ；而 则利用通过 Issuer 解析出的带外可信身份提供商（IdP）凭证，对这些断言的 进行验证，而非使用文档内部提供的密钥。 在验证过程中， 会从共享的 DOM 中移除被包裹的签名

CVSS 8.1 · High
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I. Basic Information for CVE-2026-63182

Vulnerability Information
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Vulnerability Title
LightSAML: Signature reference wrapping permits unsigned assertion claims
Source: CVE Program / CVE List V5
Vulnerability Description
LightSAML implements SAML 2.0 data model classes, XML serialization and deserialization, XML security, certificate support, and message bindings. Prior to 4.7.1 and 5.0.1, LightSAML and xmlseclibs disagree about which assertion an inbound SAML signature covers. `Response::deserialize` uses `manyElementsFromXml` to collect only direct-child `saml:Assertion` elements of `samlp:Response`, and `AssertionSignatureValidatorAction` validates their `ds:Signature` using an out-of-band trusted IdP credential resolved by Issuer, not a key from the document. `XMLSecurityDSig::validateReference()` removes the enveloped signature from the shared DOM, but `processRefNode()` resolves `Reference URI="#id"` document-wide through an XPath of the form `//*[@Id]` and takes `item(0)`, which need not be the assertion whose claims LightSAML consumes. An attacker who has captured one genuinely signed assertion, such as an earlier login response, can place its signature-stripped bytes earlier in `samlp:Extensions` and present a forged direct-child assertion with the same ID and copied genuine signature. Validation then covers the hidden genuine bytes while LightSAML surfaces unsigned attacker-controlled `Subject/NameID`, `Conditions`, and `Attributes`, enabling authentication bypass or privilege escalation even when signature validation is required. The behavior was confirmed in versions 5.0.0 and 4.6.1. This issue is fixed in versions 4.7.1 and 5.0.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
密码学签名的验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
litesaml lightsaml < 4.7.1 -

II. Public POCs for CVE-2026-63182

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III. Intelligence Information for CVE-2026-63182

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Patches & Fixes for CVE-2026-63182 (4)

Vendor Advisories for CVE-2026-63182 (1)

Vendor Pages for CVE-2026-63182 (2)

IV. Related Vulnerabilities

Same weakness: CWE-347