CVE-2026-55428: Coder incorrect authorization in tailnet coordinator AllowedIPs validation

CVE-2026-55428 · Severity: high · CVSS 8.2 · Published 2026-07-08

Coder is a platform used by organizations to manage remote development environments. A security flaw in how the system handles internal networking allows a malicious agent to impersonate other development workspaces. This could enable an attacker to intercept private data or sessions intended for a different user's workspace.

Technologies: Coder, github.com/coder/coder (Go), github.com/coder/coder/v2 (Go). Vendors: Coder, Go.

Quick answers

Is CVE-2026-55428 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55428 being exploited in the wild.
How severe is CVE-2026-55428?
High severity, with a CVSS score of 8.2, published 8 July 2026.
Which products and versions are affected?
Coder < 2.29.17, >= 2.30.0 < 2.32.7, >= 2.33.0 < 2.33.8, >= 2.34.0 < 2.34.2; github.com/coder/coder (Go) SEMVER:introduced=0; github.com/coder/coder/v2 (Go) SEMVER:introduced=0,fixed=2.29.17,introduced=2.30.0,fixed=2.32.7,introduced=2.33.0,fixed=2.33.8,introduced=2.34.0,fixed=2.34.2, SEMVER:introduced=2.34.0,fixed=2.34.2.
Is there a fix for CVE-2026-55428?
Yes. github.com/coder/coder/v2 (Go): upgrade to 2.34.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-55428 attacked?
It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-55428?
Check whether you run Coder, github.com/coder/coder (Go) or github.com/coder/coder/v2 (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/coder/coder/v2 (Go): upgrade to 2.34.2 or later
    go get github.com/coder/coder/v2@v2.34.2

Technical details

An improper authorization vulnerability exists in Coder's tailnet coordinator. While the coordinator validates that an agent's 'Addresses' derive from its authenticated UUID, it fails to apply the same check to 'AllowedIPs'. These values are forwarded verbatim to tunnel peers and installed into WireGuard configurations. A malicious agent can advertise a victim agent's IP prefix, causing the server to route traffic intended for the victim to the attacker instead. This allows for session interception between workspaces. The issue is fixed by applying UUID-derivation validation to the 'AllowedIPs' field in both the in-memory and Postgres coordinators.

Affected products

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

Identifiers

  • CVE-2026-55428
  • GHSA-wrq8-fcv5-8hvp
  • GO-2026-5915

Timeline

  • 2026-06-11: patched: Fix merged into main branch
  • 2026-07-08: disclosed: NVD publication date

References

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