better-auth: Use of a Broken or Risky Cryptographic Algorithm
CVE-2026-67336 is a high-severity use of a broken or risky cryptographic algorithm vulnerability in better-auth, with a CVSS 3.1 base score of 8.7 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 1.6.11 as the first without the flaw, so updating better-auth to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.24% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update better-auth to 1.6.11 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Better-auth | better-auth | before 1.6.11 | 1.6.11 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 9.4 | Critical | CNA (vulncheck.com) |
| CVSS 3.1 | 8.7 | High | CNA (vulncheck.com) |
Official description
better-auth versions before 1.6.11 contain insecure cryptographic defaults in the oidcProvider and mcp plugins that advertise the none algorithm and accept plain PKCE by default. Attackers can exploit algorithm negotiation to accept unsigned tokens or intercept authorization codes when PKCE plain is used instead of the required S256 method.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use of a Broken or Risky Cryptographic Algorithm
The product uses a broken or risky cryptographic algorithm or protocol.
How developers prevent this class of flaw
- Ensure that the design allows one cryptographic algorithm to be replaced with another in the next generation or version. Where possible, use wrappers to make the interfaces uniform. This will make it easier to upgrade to stronger algorithms. With hardware, design the product at the Intellectual Property (IP) level so that one cryptographic algorithm can be replaced with another in the next generation of the hardware product.
- Carefully manage and protect cryptographic keys (see CWE-320). If the keys can be guessed or stolen, then the strength of the cryptography itself is irrelevant.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Industry-standard implementations will save development time and may be more likely to avoid errors that can occur during implementation of cryptographic algorithms. Consider the ESAPI Encryption feature.
More Use of a Broken or Risky Cryptographic Algorithm vulnerabilities (CWE-327)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in better-auth
- 9.1 Critical severity
- 9.1 Critical severity
- 7.4 High severity
- 9.1 Critical severity
- 8.1 High severity
- 8.6 High severity
Recent Use of a Broken or Risky Cryptographic Algorithm vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 9.8 Critical severity
- 7.0 High severity
- 7.4 High severity
- 9.1 Critical severity
Spotted an error? Tell us.