CVE-2026-67336Network attack vectorHinoki check available

Unsigned-token acceptance via insecure OIDC defaults

Published Aug 1, 2026 · Updated Aug 1, 2026

Insecure cryptographic defaults in Better Auth before 1.6.11 allow remote attackers to forge tokens or intercept authorization codes. The legacy oidcProvider and mcp metadata builders advertise alg=none, while the authorize handler accepts plain PKCE and rewrites a missing challenge method to plain. Exploitation requires an enabled legacy plugin plus either metadata-driven algorithm negotiation or exposure of an authorization URL containing a plain challenge.

CVSS severity9.4
Critical
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Insecure cryptographic defaults in Better Auth before 1.6.11 allow remote attackers to forge tokens or intercept authorization codes. The legacy oidcProvider and mcp metadata builders advertise alg=none, while the authorize handler accepts plain PKCE and rewrites a missing challenge method to plain. Exploitation requires an enabled legacy plugin plus either metadata-driven algorithm negotiation or exposure of an authorization URL containing a plain challenge.

The record

CVE
CVE-2026-67336
Published
Aug 1, 2026
Updated
Aug 1, 2026
Vendor
Better Auth
Product
Better Auth
Classifications
CWE-327, CWE-757, CWE-1188, T1606
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <1.6.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Better Auth · Better Authversion=0 <1.6.11

Published CVSS scores

8.7VulnCheckCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
9.4VulnCheckCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
8.7Better AuthCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-327Use of a Broken or Risky Cryptographic Algorithm
CWE-757Selection of Less-Secure Algorithm During Negotiation
CWE-1188Initialization of a Resource with an Insecure Default
T1606Forge Web Credentials

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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