EUVD-2026-43306
GHSA-xv9c-v5pw-jxvf
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/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:Y/R:X/V:X/RE:M/U:Green
Primary rating from Vendor (CIRCL) · only source for this CVE.
CVSS VectorVendor: CIRCL
Lifecycle Timeline
2DescriptionCVE.org
A Server-Side Request Forgery (SSRF) protection bypass existed in the html_to_markdown expansion module of misp-modules.
The module attempts to prevent requests to loopback, private, link-local, and other restricted IP address ranges. However, IP addresses were compared against the blocked ranges without first normalising IPv4-mapped IPv6 addresses.
An authenticated attacker able to invoke the module could supply an IPv4-mapped IPv6 address, such as:
http://[::ffff:127.0.0.1]/ http://[::ffff:169.254.169.254]/
Alternatively, the attacker could use a hostname that resolves to an IPv4-mapped IPv6 address. These addresses were treated as IPv6 addresses and therefore did not match the corresponding blocked IPv4 ranges.
Successful exploitation could cause the misp-modules server to connect to services available through its loopback interface, internal network, or link-local network. This could expose internal web services, administrative interfaces, or cloud instance metadata, with retrieved content potentially returned to the attacker as converted Markdown.
The vulnerability has been addressed by normalising IPv4-mapped IPv6 addresses to their underlying IPv4 representation before applying the blocked-range checks. URLs without a valid hostname are now also rejected.
AnalysisAI
Server-Side Request Forgery bypass in the html_to_markdown expansion module of misp-modules lets an authenticated attacker reach internal, loopback, and link-local services that the module's IP range filtering was meant to block. By supplying an IPv4-mapped IPv6 address such as http://[::ffff:169.254.169.254]/ (or a hostname resolving to one), the attacker defeats the blocked-range checks and can pull back internal content — including cloud instance metadata — rendered back to them as Markdown. No public exploit identified at time of analysis and it is not in CISA KEV, but the underlying IPv4-mapped-IPv6 filter bypass is a well-understood, easily reproduced technique.
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Same weakness CWE-918 – Server-Side Request Forgery (SSRF)
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External POC / Exploit Code
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