{"id":"CVE-2026-112991","kind":"vulnerability","aliases":["CVE-2026-112991"],"related":[],"title":"MISP Modules: html_to_markdown SSRF reaches internal address ranges","description":"The html_to_markdown expansion module in MISP Modules contains a server-side request forgery (SSRF) vulnerability in its is_safe_url() URL validation function. The BLOCKED_RANGES list used to reject unsafe destination addresses was incomplete, omitting several critical IP address ranges. Specifically, the following ranges were not blocked: 0.0.0.0/8 (unspecified, which routes to loopback on Linux), 100.64.0.0/10 (carrier-grade NAT per RFC 6598), ::/128 (IPv6 unspecified), fc00::/7 (IPv6 Unique Local Addresses), and fe80::/10 (IPv6 link-local). The existing list only covered IPv4 loopback (127.0.0.0/8), RFC 1918 private ranges, IPv4 link-local (169.254.0.0/16), and IPv6 loopback (::1/128).\n\nAn authenticated user with the ability to create or modify MISP attributes that trigger the html_to_markdown expansion module could supply URLs pointing to these unblocked internal address ranges. Because the module fetches the URL server-side to convert HTML content to Markdown, the request is made from the MISP server's network context. This allows an attacker to probe and read responses from internal services, carrier-grade NAT infrastructure, or link-local endpoints that would otherwise be unreachable from external networks. IPv4-mapped IPv6 forms (e.g., [::ffff:0.0.0.0]) also bypassed the existing checks.\n\nThe security impact is primarily confidentiality: an attacker can read data served by internal services reachable from the MISP server. The MISP instance itself is not compromised, but it is abused as a proxy to access otherwise restricted network resources.","summary":"The html_to_markdown expansion module in MISP Modules fetches user-supplied URLs server-side, but its is_safe_url() blocklist misses several ranges including 0.0.0.0/8, 100.64.0.0/10, ::/128, fc00::/7, fe80::/10 and IPv4-mapped IPv6 forms. An authenticated user who can create or modify attributes that trigger the module can make the MISP server request internal services and read the responses.","severity":"medium","cvss":6.3,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["misp","misp-modules","package","self-hosted","threat-intel"],"not_affected_if":["module-disabled","trusted-users-only"],"how_to_check":"- Check the MISP Modules version installed (`pip show misp-modules` or the container image tag) and compare it with the fixed release, which the sources do not name.\n- Check whether the `html_to_markdown` expansion module is enabled in the MISP Modules configuration (unknown from sources).","fix":"- Upgrade MISP Modules to a release that extends BLOCKED_RANGES in is_safe_url() (fixed version: unknown from sources).\n- Until patched, disable the `html_to_markdown` expansion module or restrict who can create or modify attributes.","status":"open","published_at":"2026-10-19T23:17:36+00:00","first_seen_at":"2026-10-23T21:57:19+00:00","triaged_at":"2026-10-25T04:01:43+00:00","updated_at":"2026-10-25T04:01:43+00:00","category":"package","confidence":0.6,"triage":{"at":"2026-10-25T04:01:43Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade MISP Modules to a release that extends BLOCKED_RANGES in is_safe_url() (fixed version: unknown from sources).\n- Until patched, disable the `html_to_markdown` expansion module or restrict who can create or modify attributes.","reach":"network","title":"MISP Modules: html_to_markdown SSRF reaches internal address ranges","impact":"medium","summary":"The html_to_markdown expansion module in MISP Modules fetches user-supplied URLs server-side, but its is_safe_url() blocklist misses several ranges including 0.0.0.0/8, 100.64.0.0/10, ::/128, fc00::/7, fe80::/10 and IPv4-mapped IPv6 forms. An authenticated user who can create or modify attributes that trigger the module can make the MISP server request internal services and read the responses.","category":"package","nicknames":[],"who_cares":["misp","misp-modules","self-hosted","threat-intel"],"confidence":0.6,"needs_auth":"yes","worst_case":"Attacker reads responses from internal services reachable by the MISP server","analyst_note":"Find the fixed MISP Modules version and the advisory/commit at the NVD link or the MISP project repository; confirm whether the module is enabled by default.","how_to_check":"- Check the MISP Modules version installed (`pip show misp-modules` or the container image tag) and compare it with the fixed release, which the sources do not name.\n- Check whether the `html_to_markdown` expansion module is enabled in the MISP Modules configuration (unknown from sources).","needs_analyst":true,"not_affected_if":["module-disabled","trusted-users-only"],"who_is_affected":"Teams running MISP with the MISP Modules service and the html_to_markdown expansion module enabled, where users can create or edit attributes that trigger it. The MISP server's network position determines what is reachable, so instances with internal services or cloud metadata endpoints on the same network matter most. Instances without the module enabled, or where only trusted administrators can edit attributes, can skip it.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"medium"},"cost_usd":0.000752,"input_tokens":3803,"output_tokens":744,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-112991':13A,16A '-2026':12A,15A '/10':58B,63B,156C,175C '/128':59B,164C '/16':198C '/7':61B,168C '/8':56B,147C,188C '0.0.0.0':55B,146C,296C '1/128':202C '100.64.0.0':57B,155C '127.0.0.0':187C '169.254.0.0':197C '1918':190C '6598':163C 'abil':208C 'abus':332C 'access':337C 'address':9A,130C,137C,172C,231C 'allow':260C 'also':297C 'attack':262C,309C 'attribut':78B,214C 'authent':71B,204C 'block':122C,145C 'blocklist':50B 'bypass':298C 'carrier':158C,272C 'carrier-grad':157C,271C 'check':301C 'compromis':328C 'confidenti':307C 'contain':104C 'content':245C 'context':258C 'convert':243C 'could':223C 'cover':184C 'creat':75B,210C 'critic':135C 'cve':11A,14A 'data':312C 'destin':129C 'e.g':294C 'endpoint':280C 'exist':181C,300C 'expans':32B,99C,221C 'extern':287C 'fc00':60B,167C 'fe80':62B,174C 'fetch':37B,236C 'ffff':295C 'follow':141C 'forgeri':110C 'form':69B,293C 'function':120C 'grade':159C,273C 'host':24B 'html':3A,29B,96C,218C,244C 'impact':304C 'includ':54B 'incomplet':132C 'infrastructur':275C 'instanc':324C 'intel':27B 'intern':8A,89B,230C,269C,315C 'ip':136C 'ipv4':66B,185C,193C,290C 'ipv4-mapped':65B,289C 'ipv6':68B,165C,169C,176C,200C,292C 'link':178C,195C,278C 'link-loc':177C,194C,277C 'linux':154C 'list':124C,182C 'local':171C,179C,196C,279C 'loopback':152C,186C,201C 'made':251C 'make':84B 'map':67B,291C 'markdown':5A,31B,98C,220C,247C 'misp':1A,17B,19B,35B,86B,102C,213C,254C,320C,323C 'misp-modul':18B 'miss':51B 'modifi':77B,212C 'modul':2A,20B,33B,36B,82B,100C,103C,222C,235C 'nat':160C,274C 'network':257C,288C,340C 'omit':133C 'otherwis':283C,338C 'packag':21B 'per':161C 'point':226C 'primarili':306C 'privat':191C 'probe':264C 'proxi':335C 'rang':10A,53B,123C,138C,142C,192C,232C 'reach':7A 'reachabl':317C 'read':92B,266C,311C 'reject':127C 'request':88B,109C,249C 'resourc':341C 'respons':94B,267C 'restrict':339C 'rfc':162C,189C 'rout':150C 'safe':48B,116C 'secur':303C 'self':23B 'self-host':22B 'serv':313C 'server':43B,87B,107C,240C,255C,321C 'server-sid':42B,106C,239C 'servic':90B,270C,316C 'sever':52B,134C 'side':44B,108C,241C 'specif':139C 'ssrf':6A,111C 'suppli':40B,224C 'threat':26B 'threat-intel':25B 'trigger':80B,216C 'unblock':229C 'uniqu':170C 'unreach':285C 'unsaf':128C 'unspecifi':148C,166C 'url':41B,49B,117C,118C,225C,238C 'use':125C 'user':39B,72B,205C 'user-suppli':38B 'valid':119C 'vulner':112C 'would':282C","nicknames":[],"mitigations":[],"who_affected":"Teams running MISP with the MISP Modules service and the html_to_markdown expansion module enabled, where users can create or edit attributes that trigger it. The MISP server's network position determines what is reachable, so instances with internal services or cloud metadata endpoints on the same network matter most. Instances without the module enabled, or where only trusted administrators can edit attributes, can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-19T23:17:36+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/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:X/R:X/V:X/RE:X/U:X","cvss_by":"5a6e4751-2f3f-4070-9419-94fb35b644e8","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-112991","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-112991","severity":null,"published_at":"2026-10-19T23:17:36+00:00","modified_at":"2026-10-20T20:17:16+00:00","first_seen_at":"2026-10-23T21:57:19+00:00","fetched_at":"2026-10-23T22:28:57+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}