# GHSA-mpcw-3j5p-p99x: Butterfly's parseJSON, getJSON functions eval malicious input, leading to remote code execution (RCE) > Attackers can execute arbitrary code on the server by exploiting a flaw in the Butterfly library's JSON parsing functions that allows bypassing input sanitization. - **Severity:** Not scored - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 24 Oct 2024 ## What is GHSA-mpcw-3j5p-p99x? GHSA-mpcw-3j5p-p99x is a code injection vulnerability in org.openrefine.dependencies:butterfly, published on 24 Oct 2024. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description ### Summary Usage of the `Butterfly.prototype.parseJSON` or `getJSON` functions on an attacker-controlled crafted input string allows the attacker to execute arbitrary JavaScript code on the server. Since Butterfly JavaScript code has access to Java classes, it can run arbitrary programs. ### Details The `parseJSON` function (edu/mit/simile/butterfly/Butterfly.js:64) works by calling `eval`, an approach that goes back to the original library by Crockford, before JSON was part of the ECMAScript language. It uses a regular expression to remove strings from the input, then checks that there are no unexpected characters in the non-string remainder. However, the regex is imperfect, as was [discovered earlier by Mike Samuel](https://dev.to/mikesamuel/2008-silently-securing-jsonparse-5cbb); specifically, the "cleaner" can be tricked into treating part of the input as a string that the "evaluator" does not, because of a difference in interpretation regarding the [the Unicode zero-width joiner character](https://unicode-explorer.com/c/200D). Representing that character with a visible symbol, a malicious input looks like: ```js "\�\", Packages.java.lang.Runtime.getRuntime().exec('gnome-calculator')) // " ``` This is understood... * by `JSON_cleaning_RE` as a single string, and because it is a string it can be collapsed to nothing, which is not problematic, so the original input proceeds to `eval`. * by the `eval` function, which ignores zero-width joiners entirely, as a string containing a single escaped backslash, followed by a comma, then a function call, closing parenthesis, and finally a line comment. The function call is evaluated, and a calculator is opened. Possible mitigations and additional defenses could include: * Replacing the JSON implementation with Rhino's built-in implementation. * Dropping all JSON-related and JSONP-related code entirely. * Restricting the access the JavaScript controller code has to the rest of the system by using `initSafeStandardObjects` instead of `initStandardObjects`, using `setClassShutter`, and so on. ### PoC Change OpenRefine `core` `controller.js` to add a call to the vulnerable `getJSON` function: ```diff diff --git a/main/webapp/modules/core/MOD-INF/controller.js b/main/webapp/modules/core/MOD-INF/controller.js index 4ceba0676..1ce0936d2 100644 --- a/main/webapp/modules/core/MOD-INF/controller.js +++ b/main/webapp/modules/core/MOD-INF/controller.js @@ -631,0 +632,5 @@ function process(path, request, response) { + if (path == "getjsontest") { + butterfly.getJSON(request); + return true; + } + ``` Then, restart OpenRefine and submit the malicious request. For example, the following `bash` command (with $' quoting) should do it: ``` curl -H 'Content-Type: application/json;charset=utf-8' --data $'"\\\u200d\\", Packages.java.lang.Runtime.getRuntime().exec(\'gnome-calculator\')) // "' http://localhost:3333/getjsontest ``` ### Impact Any JavaScript controller that calls one of these functions is vulnerable to remote code execution. OpenRefine itself seems unaffected; both OpenRefine and jQuery have their own functions also called parseJSON and getJSON, but those are unrelated. ## Which versions are affected by GHSA-mpcw-3j5p-p99x? 2 open source packages ship an affected version, including org.openrefine.dependencies:butterfly. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `org.openrefine.dependencies:butterfly` | Maven | All versions | 1.2.6 | | `org.openrefine.dependencies:butterfly` | Maven | All versions | 1.2.6 | ## How do I fix GHSA-mpcw-3j5p-p99x? Upgrade org.openrefine.dependencies:butterfly to 1.2.6 or later. ## Is GHSA-mpcw-3j5p-p99x being exploited? There is no known exploitation of GHSA-mpcw-3j5p-p99x in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for GHSA-mpcw-3j5p-p99x and fix it if it is affected. What it is: GHSA-mpcw-3j5p-p99x is a code injection vulnerability in org.openrefine.dependencies:butterfly, published on 24 Oct 2024. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of GHSA-mpcw-3j5p-p99x in the wild and no public exploit code. Affected packages and fixed versions: - org.openrefine.dependencies:butterfly (Maven): affected all versions; fixed in 1.2.6 - org.openrefine.dependencies:butterfly (Maven): affected all versions; fixed in 1.2.6 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/GHSA-mpcw-3j5p-p99x/ (Markdown: https://insights.sbomify.com/GHSA-mpcw-3j5p-p99x/index.md) ``` ## Sources - OSV: https://osv.dev/vulnerability/GHSA-mpcw-3j5p-p99x --- From sbomify Insights: https://insights.sbomify.com/GHSA-mpcw-3j5p-p99x/ Summaries are generated and may contain mistakes; the official description above is the record.