Skip to content

Coder's OIDC email_verified type coercion bypass enables account takeover via unverified email linking

High severity GitHub Reviewed Published Jun 12, 2026 in coder/coder • Updated Jul 6, 2026

Package

gomod github.com/coder/coder/v2 (Go)

Affected versions

>= 2.34.0, < 2.34.2
>= 2.33.0, < 2.33.8
>= 2.30.0, < 2.32.7
< 2.29.17

Patched versions

2.34.2
2.33.8
2.32.7
2.29.17

Description

Summary

Coder's OIDC callback checked email_verified with a direct Go bool type assertion. When an IdP returned the claim as a non-boolean (for example the string "false") or omitted it, the assertion failed open and the email was treated as verified. Combined with an unconditional email-based account fallback, this enabled account takeover.

Impact

An attacker who registered a victim's email at a compatible IdP without verifying it could log in via OIDC and be matched to the victim's existing Coder account, receiving a session for that account. No prior authentication to Coder was required and the result was full account takeover.

Patches

The fix coerces email_verified across bool, string and numeric types (fail-closed) and blocks the email fallback when the matched user already has a different linked IdP subject.

The fix was backported to all supported release lines:

Release line Patched version
2.34 v2.34.2
2.33 v2.33.8
2.32 v2.32.7
2.29 (ESR) v2.29.17

Workarounds

Ensure the IdP returns email_verified as a native JSON boolean. The email-fallback linking issue has no configuration workaround; upgrading is required.

Resources

  • Fix: #25712, #25713

Credits

Coder would like to thank Anthropic's Security Team (ANT-2026-22444) for independently disclosing this issue!

References

@jdomeracki-coder jdomeracki-coder published to coder/coder Jun 12, 2026
Published to the GitHub Advisory Database Jul 6, 2026
Reviewed Jul 6, 2026
Last updated Jul 6, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(40th percentile)

Weaknesses

Improper Authentication

When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Learn more on MITRE.

Incorrect Type Conversion or Cast

The product does not correctly convert an object, resource, or structure from one type to a different type. Learn more on MITRE.

CVE ID

CVE-2026-55076

GHSA ID

GHSA-75vm-6w67-gwvp

Source code

Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.