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Graph/rbash-restricted-bypass-via-shell-injection

AntiPattern

Rbash Bypass via Injection

rbash-restricted-bypass-via-shell-injection

Command construction and environment variable injection let an rbash-restricted shell reach execvp('/bin/sh','-c',…) and arbitrary binaries, bypassing restricted-mode checks and populating command tables. The stakes are remote code execution and shell-policy evasion.

Node Details

Public graph metadata

Updated7/31/2026

Connections

30 linked nodes

MATCHESSolution

Split challenge data into public metadata and private scoring data — The sandbox binds the target source repo into a temporary workspace and binds only the generated MCP config. Tension: the benchmark package path with a tmpfs mount. Outcome: Added a disable switch for environments that cannot run the sandbox.

MATCHESSolution

testing that `pgdump` line by itself inside an interactive docker container issuing a `bash` command. Outcome: Once inside the temporary docker container, run command in bash shell.

MATCHESSolution

./node_modules/.bin/env-subset. Outcome: Now you can run.

MATCHESSolution

Try using `| bash -` instead of `| sh -`. Outcome: `curl -fsSL https://get.pnpm.io/install.sh | bash -`.

MATCHESSolution

passing health checks but its Bash cutover and post-cutover verification scripts exited early or misreported failure — Bash cutover and post-cutover verification scripts. Tension: post-increment arithmetic such as `((elapsed++))` / `((PASS_COUNT++))`, brittle command-output parsing for npm preflight status, and exact JSON-shape assumptions for RPC verification.

MATCHESSolution

My solution was to install rsync directly into Git-Bash environment and forgo cygwin altogether — remote windows machine. Tension: existing installation of Git-Bash on the remote windows machine conflicting with the new installation of cygwin. Outcome: Basically following the instructions found here: https://stackoverflow.com/a/76843477/4556955.

MATCHESSolution

Avoid deploying to the same host as the self-hosted runner; instead use separate infrastructure or safer deployment approaches (e.g., GitHub Environments/Deployments) and restrict runner permissions/isolate the runner from application runtime.

MATCHESSolution

Normally, you could have just passed the parameters to `aws` in your `CMD`, but since you're substituting environment variables, you'll need to run a shell. — you'll need to run a shell. Tension: since you're substituting environment variables. Outcome: ENTRYPOINT sh -c "aws s3 sync /build s3://${BUCKET_NAME} --delete".

MATCHESSolution

Run the student code in a restricted environment while the verification code runs in a separate un-restricted environment. Tension: there's no trust boundary between the student's function and the verification code. Outcome: Untrusted or unreliable code runs in a separate process with limited access.

MATCHESSolution

Restrict or audit grants of DBA/other powerful roles to accounts that can invoke invoker-rights code, and limit who can execute invoker-rights functions (avoid granting execute to PUBLIC). Prefer safer security patterns (e.g., definer-rights with controlled privileges, or using least-privilege accounts and tightening execution grants) and apply relevant Oracle security patches/workarounds for the known invoker-rights privilege inheritance behavior.

MATCHESSolution

Use a shell wrapper only if shell metacharacters are intended, otherwise pass arguments as a command array and avoid shell parsing

MATCHESSolution

`load` is still available. — if I set `os` and `io` to `nil` before running the script. Tension: will it completely prevent user from gaining access to those standard libraries? Outcome: This will allow loading malicious bytecode.

MATCHESSolution

Use the appropriate repository role that permits bypassing branch protections (and accept that it conflicts with the 'Do not allow bypassing…' setting for this scenario). Alternatively, upgrade to/enable the paid branch protection capability ('Restrict who can push to matching branches') so you can control bypass behavior per user/team.

MATCHESSolution

Open PowerShell (admin), check the current execution policy with `Get-ExecutionPolicy`, and if restricted, set it for the current user to `RemoteSigned` (e.g., `Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy RemoteSigned`), then retry the `npx` command.

MATCHESSolution

Change line 361 from `if (posixly_correct == 0 || legal_identifier(name))` to `if (legal_identifier(name))` — This ensures that variable names used as function definitions always contain only legal shell identifier characters. Tension: preventing injection of shell metacharacters. Outcome: The variable name must pass validation before being concatenated into the command string that will be parsed and executed.

MATCHESSolution

Make the primary install command prompt securely via `/dev/tty` (`curl ... | bash`) — The install instructions also pushed users toward passing an API key inline. Tension: keep `--key` as an optional low-friction path.

MATCHESSolution

The vulnerability requires validating that function definition variables contain ONLY a valid function definition. — Bash 4.4+ includes a proper fix by validating function definitions during the parsing phase. Tension: The parser was modified to reject function definitions that have trailing code after the closing brace.

MATCHESSolution

any commands appended after the function in the same env-var value are executed unconditionally during shell init — environment variables that begin with the literal prefix '() {' as exported function definitions during shell startup. Tension: Env vars are routinely populated from untrusted sources. Outcome: pre-auth RCE.

MATCHESSolution

Patch: Change enable.def line 165 — builtins/enable.def. Tension: This blocks enable -f even during the startup file window where restricted == 0 but restricted_shell == 1. Outcome: if ((restricted || restricted_shell) && (flags & (FFLAG|DFLAG))).

MATCHESSolution

unbounded memory allocation (DoS) — processing a crafted ELF file.

MATCHESSolution

Outcome: split server_cmd on whitespace and use execvp directly with argv[] instead of 'sh -c server_cmd'.

MATCHESSolution

The vulnerability requires post-expansion path normalization and validation. — After concatenating the home directory with the user-supplied path component (line 82). Outcome: replace the blind memcpy with a validated copy that checks for path traversal sequences, or use realpath()/canonical path functions after concatenation.

MATCHESSolution

fixed pre-bash-4.4-beta2 in variables.c:assign_hashcmd lines 1764-1785 — Bash <= 5.0 restricted shell (rbash). Tension: restricted shell (rbash) can be bypassed.

MATCHESSolution

before `ijs_invoke_server(ijsdev->IjsServer)`. Tension: This re-applies the --permit-file-write allowlist that the IJS off-ramp currently skips. Outcome: stop using `execvp("sh","-c",server_cmd)`.

MATCHESSolution

The durable fix moved function imports under a distinct env-var prefix `BASH_FUNC_name%%` — Upstream remediation evolved across multiple patches. Tension: ad-hoc string checks proved insufficient. Outcome: the function importer is a separate, dedicated parser and the general env loop never feeds attacker text to parse_and_execute.

MATCHESSolution

The vulnerability can be fixed by sanitizing the fname parameter before passing to popen(). Tension: Validate that fname contains only safe characters and reject filenames containing shell metacharacters (|, ;, &, $, backtick, etc.). Outcome: Alternatively, use posix_spawn() with execv array instead of popen() to avoid shell interpretation entirely. The most secure solution is to disable the pipe device by default and require an explicit security flag to enable it.

MATCHESSolution

Shell-quote outname in do_ed_script before the sprintf — do_ed_script() at pch.c:2399-2403. Tension: avoid shell interpretation entirely.

MATCHESSolution

Found vulnerability through source code audit of coreutils-8.20 — key files examined: src/sort.c. Tension: the issue.

MATCHESSolution

ONE tool: bash(command). — local models (qwen3). Tension: No tool-selection decision fatigue. Outcome: Orchestrator handles inErrata calls externally.

MATCHESSolution

replace the direct concatenation with a properly quoted version — The patch codebase already has a quotearg() function available for this purpose. Tension: avoid shell interpretation entirely by using execvp() with a pre-constructed argv array instead of popen() with a shell command string.

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