{"id":"CVE-2026-55431","aliases":["GHSA-v54h-cp2w-9x4g","GO-2026-5924"],"url":"https://o3.security/vulnerability/CVE-2026-55431","summary":"Coder's session token leaked to arbitrary hosts via `coder open app` for external workspace apps","details":"Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, `coder open app` opens external workspace-app URLs without validating the scheme or host. When an external app URL contains the `$SESSION_TOKEN` placeholder the CLI replaces it with the user's real session token before handing the URL to the OS open handler. Practical exploitation requires the victim to run `coder open app` against a workspace whose external app definition the attacker controls. Only a malicious template author can control external app URLs. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 applies a URL-scheme allowlist in the CLI and limits `$SESSION_TOKEN` substitution to trusted destinations like the web frontend. As a workaround, avoid running `coder open app` for untrusted workspaces.","published":"2026-07-08T00:10:49.165Z","modified":"2026-08-12T03:51:19.846523250Z","cvss":{"score":7.7,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N"},"epss":{"score":0.00183,"percentile":0.08155,"asOf":"2026-08-21"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/coder/coder/v2","fixedVersion":"2.34.2"},{"ecosystem":"Go","name":"github.com/coder/coder/v2","fixedVersion":"2.33.8"},{"ecosystem":"Go","name":"github.com/coder/coder/v2","fixedVersion":"2.32.7"},{"ecosystem":"Go","name":"github.com/coder/coder/v2","fixedVersion":"2.29.17"}],"fix":{"url":"https://github.com/coder/coder/pull/26146","label":"coder/coder#26146"},"references":[{"type":"WEB","url":"https://github.com/coder/coder/releases/tag/v2.29.17"},{"type":"WEB","url":"https://github.com/coder/coder/releases/tag/v2.32.7"},{"type":"WEB","url":"https://github.com/coder/coder/releases/tag/v2.33.8"},{"type":"WEB","url":"https://github.com/coder/coder/releases/tag/v2.34.2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55431.json"},{"type":"ADVISORY","url":"https://github.com/coder/coder/security/advisories/GHSA-v54h-cp2w-9x4g"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55431"},{"type":"FIX","url":"https://github.com/coder/coder/pull/26146"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:19.846523250Z"}}