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CVE-2026-40280— Gotenberg SSRF via case-insensitive URL scheme bypass in webhook and downloadFrom deny-lists

Quick assessment

Affected
gotenberg gotenberg
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Gotenberg是Gotenberg开源的一个开发人员友好的 API。用于将多种文档格式转换为 PDF 文件。 Gotenberg 8.30.1及之前版本存在代码问题漏洞，该漏洞源于默认私有IP拒绝列表使用区分大小写的正则表达式匹配URL方案，可能导致绕过拒绝列表并访问内部网络服务。

AI Predicted 7.5 Difficulty: Easy EPSS 2.11% · P81

Public Exploits 1

Nuclei · 1 CVE-2026-40280.yaml [template]

Affected Version Matrix 1

VendorProduct Version RangeStatus
gotenberg gotenberg <= 8.30.1 affected
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I. Basic Information for CVE-2026-40280

Vulnerability Information
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Vulnerability Title
Gotenberg SSRF via case-insensitive URL scheme bypass in webhook and downloadFrom deny-lists
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
Gotenberg 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Gotenberg是Gotenberg开源的一个开发人员友好的 API。用于将多种文档格式转换为 PDF 文件。 Gotenberg 8.30.1及之前版本存在代码问题漏洞，该漏洞源于默认私有IP拒绝列表使用区分大小写的正则表达式匹配URL方案，可能导致绕过拒绝列表并访问内部网络服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
gotenberg gotenberg <= 8.30.1 -

II. Public POCs for CVE-2026-40280

# POC Description Source Link Shenlong Link
1 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. https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-40280.yaml POC Details
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III. Intelligence Information for CVE-2026-40280

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Patches & Fixes for CVE-2026-40280 (1)

Vendor Advisories for CVE-2026-40280 (2)

IV. Related Vulnerabilities

Same product: gotenberg
Same vendor: gotenberg
Same weakness: CWE-918

V. Comments for CVE-2026-40280

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