CVE-2026-55075: Anthropic Python — HIGH

Q: Is CVE-2026-55075 actively exploited?

No confirmed active exploitation of CVE-2026-55075 has been reported, but organizations should still patch proactively.

Q: How to fix CVE-2026-55075?

Update to patched version: Anthropic Python 2.34.2.

Q: What is the CVSS score for CVE-2026-55075?

CVE-2026-55075 has a CVSS v3.1 base score of 7.4 (HIGH).

### Summary Two flaws in Coder's OIDC login chained into account takeover: email-based user matching fell back to linking by email without checking for an existing link to a different IdP subject and the `email_verified` claim was only enforced when present as a boolean `false` so an absent or...

Full CISO analysis pending enrichment.

What systems are affected?

Package	Ecosystem	Vulnerable Range	Patched
Anthropic Python	go	>= 2.34.0, < 2.34.2	`2.34.2`
3.7K 5.4K dependents Pushed 4d ago 95% patched ~3d to patch Full package profile →

Do you use Anthropic Python? You're affected.

How severe is it?

CVSS 3.1

7.4 / 10

EPSS

N/A

Exploitation Status

No known exploitation

Sophistication

N/A

What is the attack surface?

AV Network

AC High

PR None

UI None

S Unchanged

C High

I High

A None

What should I do?

Patch available

Update Anthropic Python to version 2.34.2

Which compliance frameworks are affected?

Compliance analysis pending. Sign in for full compliance mapping when available.

Frequently Asked Questions

What is CVE-2026-55075?

### Summary Two flaws in Coder's OIDC login chained into account takeover: email-based user matching fell back to linking by email without checking for an existing link to a different IdP subject and the `email_verified` claim was only enforced when present as a boolean `false` so an absent or non-boolean claim was treated as verified. ### Impact An attacker who could authenticate at the configured OIDC provider with an email matching a victim's Coder account could log in as that victim and gain full access to their workspaces, templates and resources. This required OIDC authentication, attacker control of a matching email at the IdP and a victim account not yet linked to a different IdP subject. ### Patches The fix restricts the email fallback to first-time and legacy linking and defaults `email_verified` to false when the claim is absent or of an unexpected type. The fix was backported to all supported release lines: | Release line | Patched version | |---|---| | 2.34 | [v2.34.2](https://github.com/coder/coder/releases/tag/v2.34.2) | | 2.33 | [v2.33.8](https://github.com/coder/coder/releases/tag/v2.33.8) | | 2.32 | [v2.32.7](https://github.com/coder/coder/releases/tag/v2.32.7) | | 2.29 (ESR) | [v2.29.17](https://github.com/coder/coder/releases/tag/v2.29.17) | ### Workarounds Configure the OIDC provider to disallow self-registration or to require email verification before issuing tokens. ### Resources - Fix: #25712, #25713 ### Credits Coder would like to thank Anthropic's Security Team (ANT-2026-22450) for independently disclosing this issue!

Is CVE-2026-55075 actively exploited?

No confirmed active exploitation of CVE-2026-55075 has been reported, but organizations should still patch proactively.

How to fix CVE-2026-55075?

Update to patched version: Anthropic Python 2.34.2.

What is the CVSS score for CVE-2026-55075?

CVE-2026-55075 has a CVSS v3.1 base score of 7.4 (HIGH).

What are the technical details?

Original Advisory

### Summary Two flaws in Coder's OIDC login chained into account takeover: email-based user matching fell back to linking by email without checking for an existing link to a different IdP subject and the `email_verified` claim was only enforced when present as a boolean `false` so an absent or non-boolean claim was treated as verified. ### Impact An attacker who could authenticate at the configured OIDC provider with an email matching a victim's Coder account could log in as that victim and gain full access to their workspaces, templates and resources. This required OIDC authentication, attacker control of a matching email at the IdP and a victim account not yet linked to a different IdP subject. ### Patches The fix restricts the email fallback to first-time and legacy linking and defaults `email_verified` to false when the claim is absent or of an unexpected type. The fix was backported to all supported release lines: | Release line | Patched version | |---|---| | 2.34 | [v2.34.2](https://github.com/coder/coder/releases/tag/v2.34.2) | | 2.33 | [v2.33.8](https://github.com/coder/coder/releases/tag/v2.33.8) | | 2.32 | [v2.32.7](https://github.com/coder/coder/releases/tag/v2.32.7) | | 2.29 (ESR) | [v2.29.17](https://github.com/coder/coder/releases/tag/v2.29.17) | ### Workarounds Configure the OIDC provider to disallow self-registration or to require email verification before issuing tokens. ### Resources - Fix: #25712, #25713 ### Credits Coder would like to thank Anthropic's Security Team (ANT-2026-22450) for independently disclosing this issue!

Weaknesses (CWE)

CWE-287 Improper Authentication Primary CWE-289 Authentication Bypass by Alternate Name Primary

CWE-287 — Improper Authentication: When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.