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CVE-2026-75759— Encrypted ID token or JARM response accepted without a nested signature in erlef oidcc

Quick assessment

Affected
erlef oidcc
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.

以下是该漏洞描述的中文翻译： erlef/oidcc 中加密签名验证不当漏洞 erlef/oidcc 中存在一个“加密签名验证不当”（Improper Verification of Cryptographic Signature）漏洞，允许未认证的攻击者通过携带未嵌套签名的加密 ID Token 或 JARM 响应，冒充任意用户。根据《OpenID Connect Core 1.0》第 2 节，加密的 ID Token 应先签名再加密，最终形成嵌套 JWT；而 JARM 处理规则第 5 条要求客户端无条件地校验签

CVSS 7.6 · High

Possible ATT&CK Techniques 1 AI

T1539 · Steal Web Session Cookie
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I. Basic Information for CVE-2026-75759

Vulnerability Information
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Vulnerability Title
Encrypted ID token or JARM response accepted without a nested signature in erlef oidcc
Source: CVE Program / CVE List V5
Vulnerability Description
Improper Verification of Cryptographic Signature vulnerability in erlef oidcc allows an unauthenticated attacker to impersonate an arbitrary user via an encrypted ID token or JARM response carrying no nested signature. OpenID Connect Core 1.0 section 2 requires that an encrypted ID token be signed then encrypted, with the result being a Nested JWT, and JARM processing rule 5 requires the client to check the signature unconditionally. oidcc instead accepted a JWE wrapping unsigned claims as fully validated, so anyone holding the relying party's public encryption key could mint a token with an arbitrary sub, iss, and aud without possessing the provider's signing key. In oidcc_jwt_util:verify_decrypted_token/4, a decrypted payload that is not a signed JWS fell back to parsing the plaintext claims and returning them with no verifying key. oidcc_token:int_validate_jwt/4 then matched on the JOSE structure type rather than on whether a signature had been verified, and returned success. The JARM path in oidcc_token:validate_jarm/3 is reachable through the browser front channel. UserInfo responses are not affected, because OpenID Connect Core 1.0 section 5.3.2 permits them to be encrypted without also being signed. This issue affects oidcc: from 3.2.0-beta.1 before 3.9.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA: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
erlef oidcc 3.2.0-beta.1 ~ 3.9.0 cpe:2.3:a:erlef:oidcc:*:*:*:*:*:*:*:*
erlef oidcc 37a1361f704889816db2873f72d744d63ec39568 ~ 5f62fbccdae8526ff62653b8901657a6c1400fd9 cpe:2.3:a:erlef:oidcc:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-75759

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III. Intelligence Information for CVE-2026-75759

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Patches & Fixes for CVE-2026-75759 (1)

Vendor Advisories for CVE-2026-75759 (2)

Vendor Pages for CVE-2026-75759 (1)

IV. Related Vulnerabilities

Same product: oidcc
Same vendor: erlef
Same weakness: CWE-347

V. Comments for CVE-2026-75759

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