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.
Metrics
Affected Vendors & Products
References
History
Tue, 05 May 2026 23:15:00 +0000
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Gotenberg
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Tue, 05 May 2026 20:00:00 +0000
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| 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. | |
| Title | Gotenberg SSRF via case-insensitive URL scheme bypass in webhook and downloadFrom deny-lists | |
| Weaknesses | CWE-918 | |
| References |
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| Metrics |
cvssV4_0
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-05-05T19:52:40.327Z
Reserved: 2026-04-10T20:22:44.034Z
Link: CVE-2026-40280
No data.
Status : Received
Published: 2026-05-05T20:16:38.633
Modified: 2026-05-05T20:16:38.633
Link: CVE-2026-40280
No data.
OpenCVE Enrichment
Updated: 2026-05-05T23:00:10Z