Atlantis: OS command injection through PR-controlled Terraform workspace enables RCE during plan

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No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Atlantis is a self-hosted golang application that listens for Terraform pull request events via webhooks. From version 0.4.0 until 0.47.1, Atlantis passes the pull-request-controlled workspace value from atlantis.yaml into Terraform command arguments that are joined with strings.Join(args, " ") and executed through sh -c. An authenticated contributor whose pull request is eligible for an Atlantis plan can include shell metacharacters in the workspace name, causing arbitrary commands to execute as the Atlantis service account without custom workflows, apply permission, or a malicious Terraform provider. External contributors can reach the flaw through fork pull requests only when --allow-fork-prs is enabled, while eligible same-repository branches do not require that option. The commands inherit the Atlantis process environment and can access cloud-provider, Terraform, and version-control credentials as well as files, state, and network resources available to the service. This issue is fixed in version 0.47.1.

Source published

27 Oct 2026 17:11:12 UTC

Source modified

27 Oct 2026 17:11:12 UTC

Observed here

27 Oct 2026 18:43:43 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Atlantis is a self-hosted golang application that listens for Terraform pull request events via webhooks. From version 0.4.0 until 0.47.1, Atlantis passes the pull-request-controlled workspace value from atlantis.yaml into Terraform command arguments that are joined with strings.Join(args, " ") and executed through sh -c. An authenticated contributor whose pull request is eligible for an Atlantis plan can include shell metacharacters in the workspace name, causing arbitrary commands to execute as the Atlantis service account without custom workflows, apply permission, or a malicious Terraform provider. External contributors can reach the flaw through fork pull requests only when --allow-fork-prs is enabled, while eligible same-repository branches do not require that option. The commands inherit the Atlantis process environment and can access cloud-provider, Terraform, and version-control credentials as well as files, state, and network resources available to the service. This issue is fixed in version 0.47.1.

Source published

Oct 27, 2026, 5:11:12 PM (timezone not stated)

Source modified

Oct 27, 2026, 5:11:12 PM (timezone not stated)

Observed here

30 Oct 2026 02:00:14 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Atlantis is a self-hosted golang application that listens for Terraform pull request events via webhooks. From version 0.4.0 until 0.47.1, Atlantis passes the pull-request-controlled workspace value from atlantis.yaml into Terraform command arguments that are joined with strings.Join(args, " ") and executed through sh -c. An authenticated contributor whose pull request is eligible for an Atlantis plan can include shell metacharacters in the workspace name, causing arbitrary commands to execute as the Atlantis service account without custom workflows, apply permission, or a malicious Terraform provider. External contributors can reach the flaw through fork pull requests only when --allow-fork-prs is enabled, while eligible same-repository branches do not require that option. The commands inherit the Atlantis process environment and can access cloud-provider, Terraform, and version-control credentials as well as files, state, and network resources available to the service. This issue is fixed in version 0.47.1.

Source published

27 Oct 2026 18:17:35 UTC

Source modified

28 Oct 2026 15:24:56 UTC

Observed here

29 Oct 2026 21:50:49 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

### Summary Atlantis passes the Terraform `workspace` value from a pull request's `atlantis.yaml` into a shell command without quoting or escaping it. A contributor whose pull request is eligible for an Atlantis plan can include shell metacharacters in the workspace name and execute arbitrary commands as the Atlantis service account. This does not require custom workflows, `allow_custom_workflows`, or permission to run `terraform apply`. The executed command inherits the Atlantis process environment, which commonly contains cloud-provider, Terraform, and VCS credentials. ### Details Verified against current `upstream/main` commit `92ce5c51d1a050357e44df3535483425e59fa984` on August 13, 2026. The vulnerable data flow is: 1. The PR-controlled project workspace is validated in [`server/core/config/raw/project.go`](https://github.com/runatlantis/atlantis/blob/92ce5c51d1a050357e44df3535483425e59fa984/server/core/config/raw/project.go#L139-L149). Validation rejects only `..`, `/`, and `\`. Shell metacharacters such as `;`, `#`, `$`, redirections, and whitespace remain permitted. 2. The workspace is passed directly as a Terraform command argument in [`server/core/runtime/workspace_step_runner_delegate.go`](https://github.com/runatlantis/atlantis/blob/92ce5c51d1a050357e44df3535483425e59fa984/server/core/runtime/workspace_step_runner_delegate.go#L86-L96): ```go []string{workspaceCmd, "select", ctx.Workspace} ``` 3. Terraform arguments are concatenated into a single string using `strings.Join(args, " ")` in [`server/core/terraform/tfclient/terraform_client.go`](https://github.com/runatlantis/atlantis/blob/92ce5c51d1a050357e44df3535483425e59fa984/server/core/terraform/tfclient/terraform_client.go#L451-L468): ```go tfCmd := fmt.Sprintf("%s %s", binPath, strings.Join(args, " ")) ``` 4. The resulting string is executed through `sh -c` in [`server/core/terraform/tfclient/terraform_client.go`](https://github.com/runatlantis/atlantis/blob/92ce5c51d1a050357e44df3535483425e59fa984/server/core/terraform/tfclient/terraform_client.go#L416-L427): ```go cmd := exec.Command("sh", "-c", tfCmd) ``` Consequently, a workspace such as: ```text poc;id;false;# ``` produces commands equivalent to: ```sh terraform workspace select poc;id;false;# terraform workspace new poc;id;false;# ``` `raw.Project.Validate()` was confirmed to return no error for this workspace value. Atlantis documents that planning untrusted Terraform can already be dangerous because providers and external data sources execute code. The distinct issue here is that an ordinary project configuration field becomes shell source, bypassing the explicit `allow_custom_workflows` control and requiring no malicious provider, external data source, custom workflow, or apply operation. The primary remediation should be to execute Terraform using an argument vector rather than constructing shell source—for example, `exec.Command(binaryPath, args...)`. Any required environment-variable expansion should be performed without invoking a shell. Strict workspace-name validation would also provide defense in depth. ### PoC Only reproduce this against a disposable Atlantis instance and test repository. #### Preconditions - Atlantis processes `atlantis.yaml` from the pull request branch. - The pull request is eligible to run `atlantis plan`. - For a fork pull request, the server must have `--allow-fork-prs` enabled. A same-repository branch does not require this flag. - No custom workflows or apply permissions are required. #### Repository contents Create `main.tf`: ```hcl terraform { required_version = ">= 1.0" } ``` Create `atlantis.yaml`: ```yaml version: 3 projects: - name: workspace-rce-poc dir: . workspace: "poc;id;false;#" autoplan: enabled: false ``` Open a pull request containing these files and comment: ```text atlantis plan -p workspace-rce-poc ``` #### Expected result Atlantis first runs `terraform workspace select`. The injected `false` causes that command invocation to return an error, so Atlantis retries using `terraform workspace new`. On both attempts, the shell executes `id` as a separate command. The second failure includes the combined command output in the Atlantis error response, exposing output similar to: ```text uid=1000(atlantis) gid=1000(atlantis) groups=1000(atlantis) ``` This demonstrates arbitrary shell-command execution without creating a custom workflow or reaching the apply phase. The payload uses only `id` and `false` and does not access credentials, make network requests, or modify the host beyond Terraform potentially creating the disposable `poc` workspace. ### Impact This is an OS command injection vulnerability resulting in remote code execution as the Atlantis service account. Affected deployments are those that: - Process pull-request-controlled `atlantis.yaml` project configuration; and - Permit the attacker-controlled pull request to trigger an Atlantis plan. Potential consequences include: - Reading and exfiltrating cloud-provider, Terraform, and VCS credentials inherited from the Atlantis process. - Accessing Terraform state, plan files, repository checkouts, caches, and other data available to the Atlantis user. - Modifying files or binaries accessible to the service account. - Making network requests using the Atlantis server's network identity. - Pivoting into infrastructure accessible through the server's credentials or network placement. For public repositories, arbitrary external contributors are directly exposed when `--allow-fork-prs` is enabled. Without fork PR support, the vulnerable population includes users able to create eligible same-repository pull requests and attackers controlling such accounts.

Source published

27 Oct 2026 21:04:50 UTC

Source modified

27 Oct 2026 21:15:03 UTC

Observed here

27 Oct 2026 21:48:52 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Publisher rating · HIGH