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CVE-2026-55735— Guardian.revoke/3 acts on unverified token claims, allowing forged-token session revocation

Quick assessment

Affected
ueberauth guardian
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.

ueberauth Guardian是ueberauth组织开源的一个基于令牌的身份验证库，可用于 Elixir 应用程序。 ueberauth Guardian 1.0.0至2.4.1之前版本存在加密问题漏洞，该漏洞源于对加密签名验证不当，Guardian.revoke/3函数在解码令牌时未验证签名，直接处理未验证的声明，可能导致未经身份验证的攻击者利用伪造令牌撤销受害者会话，造成拒绝服务。

CVSS 8.2 · High EPSS 0.46% · P38

Possible ATT&CK Techniques 1 AI

T1556.005 · Reversible Encryption

Affected Version Matrix 2

VendorProduct Version RangeStatus
ueberauth guardian 1.0.0< 2.4.1 affected
d65227145f72b290106c06cecbe42728fbf05fe2< 2bd7a8c29770d423d855c0a4965caa6c3e486901 affected
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I. Basic Information for CVE-2026-55735

Vulnerability Information
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Vulnerability Title
Guardian.revoke/3 acts on unverified token claims, allowing forged-token session revocation
Source: CVE Program / CVE List V5
Vulnerability Description
Improper Verification of Cryptographic Signature in ueberauth guardian allows an unauthenticated attacker to revoke a victim's session with a forged token. Guardian.revoke/3 in lib/guardian.ex decodes the supplied token with peek/1, which performs no signature verification (it only base64-decodes the JWT header and payload). The resulting unverified claims are forwarded directly to the configured token module's revoke callback and the implementation's on_revoke callback, a state-mutating sink. The sibling operations refresh/2 and exchange/4 both call decode_and_verify first, so the signature is checked before anything acts on the claims; revoke/3 is the only state-mutating path that acts on claims without verifying the signature. An attacker who knows or guesses a victim's identifying claim values (jti, sub) can forge a JWT carrying those claims, sign it with an arbitrary key, and submit it to any endpoint that funnels a caller-supplied token into Guardian.revoke/3 (the standard logout / session-revocation pattern). When the token module mutates state keyed by the claims (whitelist deletion or blacklist insertion, for example a GuardianDb-style store), the victim's legitimate session is evicted. This is an unauthenticated session-revocation denial of service; the attacker never needs the signing secret. This issue affects guardian: from 1.0.0 before 2.4.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/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
Vulnerability Title
ueberauth Guardian 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
ueberauth Guardian是ueberauth组织开源的一个基于令牌的身份验证库，可用于 Elixir 应用程序。 ueberauth Guardian 1.0.0至2.4.1之前版本存在加密问题漏洞，该漏洞源于对加密签名验证不当，Guardian.revoke/3函数在解码令牌时未验证签名，直接处理未验证的声明，可能导致未经身份验证的攻击者利用伪造令牌撤销受害者会话，造成拒绝服务。
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
ueberauth guardian 1.0.0 ~ 2.4.1 cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*
ueberauth guardian d65227145f72b290106c06cecbe42728fbf05fe2 ~ 2bd7a8c29770d423d855c0a4965caa6c3e486901 cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-55735

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 9436 chars
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III. Intelligence Information for CVE-2026-55735

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Patches & Fixes for CVE-2026-55735 (1)

Vendor Advisories for CVE-2026-55735 (3)

Same Patch Batch · ueberauth · 2026-08-01 · 4 CVEs total

CVE-2026-54894 6.9 MEDIUM Atom-table exhaustion denial of service in Guardian via unbounded atom creation from binar
CVE-2026-55733 6.9 MEDIUM Atom-table exhaustion denial of service in Guardian permissions AtomEncoding via unbounded
CVE-2026-55734 6.9 MEDIUM guardian atom exhaustion in Guardian.Permissions.encode_permissions!/1

IV. Related Vulnerabilities

Same product: guardian
Same vendor: ueberauth
Same weakness: CWE-347

V. Comments for CVE-2026-55735

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