{"id":"CVE-2026-123492","kind":"vulnerability","aliases":["CVE-2026-123492"],"related":[],"title":"SiYuan: MCP resource read crashes the kernel for authenticated users","description":"SiYuan before 3.8.9 contains a nil pointer dereference vulnerability in privateCacheMiddleware that allows authenticated attackers to crash the kernel by reading nonexistent MCP resources. Attackers with a valid API token can send a resources/read request in an initialized MCP session, causing a panic that terminates the kernel process and interrupts service.","summary":"SiYuan before 3.8.9 has a nil pointer dereference in privateCacheMiddleware. An attacker with a valid API token can send a resources/read request for a nonexistent MCP resource, which panics and terminates the kernel process, interrupting service.","severity":"medium","cvss":6.9,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["mcp","package","self-hosted","siyuan"],"not_affected_if":["mcp-disabled","no-api-token-access"],"how_to_check":"- Check the installed SiYuan version in the app's About panel or package metadata; versions below `3.8.9` are in range.\n- Confirm whether the MCP server is enabled and reachable by clients that hold API tokens.","fix":"- SiYuan: move to `3.8.9` or later.","status":"open","published_at":"2026-11-06T15:17:18+00:00","first_seen_at":"2026-11-06T15:42:44+00:00","triaged_at":"2026-11-06T15:44:24+00:00","updated_at":"2026-11-06T15:44:24+00:00","category":"package","confidence":0.8,"triage":{"at":"2026-11-06T15:44:24Z","model":"claude-haiku-5-5","output":{"fix":"- SiYuan: move to `3.8.9` or later.","reach":"network","title":"SiYuan: MCP resource read crashes the kernel for authenticated users","impact":"low","summary":"SiYuan before 3.8.9 has a nil pointer dereference in privateCacheMiddleware. An attacker with a valid API token can send a resources/read request for a nonexistent MCP resource, which panics and terminates the kernel process, interrupting service.","audience":"businesses","category":"package","nicknames":[],"who_cares":["siyuan","self-hosted","mcp"],"confidence":0.8,"fix_status":"available","needs_auth":"yes","worst_case":"kernel process crashes, service interrupted until restart","analyst_note":"","how_to_check":"- Check the installed SiYuan version in the app's About panel or package metadata; versions below `3.8.9` are in range.\n- Confirm whether the MCP server is enabled and reachable by clients that hold API tokens.","plain_action":"","needs_analyst":false,"not_affected_if":["no-api-token-access","mcp-disabled"],"who_is_affected":"Teams running SiYuan with its MCP server or API reachable by clients holding API tokens. An attacker needs a valid token and an initialized MCP session to trigger the crash. Single-user installs without exposed API access are less exposed.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"medium"},"cost_usd":0.000681,"input_tokens":4291,"output_tokens":503,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-123492':13A,16A '-2026':12A,15A '3.8.9':25B,61C 'allow':71C 'api':38B,87C 'attack':34B,73C,83C 'authent':9A,72C 'caus':99C 'contain':62C 'crash':5A,75C 'cve':11A,14A 'derefer':30B,66C 'host':21B 'initi':96C 'interrupt':57B,108C 'kernel':7A,55B,77C,105C 'mcp':2A,17B,48B,81C,97C 'nil':28B,64C 'nonexist':47B,80C 'packag':18B 'panic':51B,101C 'pointer':29B,65C 'privatecachemiddlewar':32B,69C 'process':56B,106C 'read':4A,79C 'request':44B,93C 'resourc':3A,49B,82C 'resources/read':43B,92C 'self':20B 'self-host':19B 'send':41B,90C 'servic':58B,109C 'session':98C 'siyuan':1A,22B,23B,59C 'termin':53B,103C 'token':39B,88C 'user':10A 'valid':37B,86C 'vulner':67C","nicknames":[],"mitigations":[],"who_affected":"Teams running SiYuan with its MCP server or API reachable by clients holding API tokens. An attacker needs a valid token and an initialized MCP session to trigger the crash. Single-user installs without exposed API access are less exposed.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["mcp","medium","package","selfhosted","siyuan"],"campaign_type":null,"search_a":"'-123492':13A,16A '-2026':12A,15A 'authent':9A 'crash':5A 'cve':11A,14A 'kernel':7A 'mcp':2A 'read':4A 'resourc':3A 'siyuan':1A 'user':10A","search_b":"'3.8.9':25B 'api':38B 'attack':34B 'derefer':30B 'host':21B 'interrupt':57B 'kernel':55B 'mcp':17B,48B 'nil':28B 'nonexist':47B 'packag':18B 'panic':51B 'pointer':29B 'privatecachemiddlewar':32B 'process':56B 'request':44B 'resourc':49B 'resources/read':43B 'self':20B 'self-host':19B 'send':41B 'servic':58B 'siyuan':22B,23B 'termin':53B 'token':39B 'valid':37B","search_c":"'3.8.9':61C 'allow':71C 'api':87C 'attack':73C,83C 'authent':72C 'caus':99C 'contain':62C 'crash':75C 'derefer':66C 'initi':96C 'interrupt':108C 'kernel':77C,105C 'mcp':81C,97C 'nil':64C 'nonexist':80C 'panic':101C 'pointer':65C 'privatecachemiddlewar':69C 'process':106C 'read':79C 'request':93C 'resourc':82C 'resources/read':92C 'send':90C 'servic':109C 'session':98C 'siyuan':59C 'termin':103C 'token':88C 'valid':86C 'vulner':67C","first_public_at":"2026-10-22T04:44:47+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/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":"disclosure@vulncheck.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-123492","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-123492","severity":null,"published_at":"2026-11-06T15:17:18+00:00","modified_at":"2026-11-06T15:17:18+00:00","first_seen_at":"2026-11-06T15:42:44+00:00","fetched_at":"2026-11-06T15:42:44+00:00","note":null}],"documents":[{"id":87564,"url":"https://github.com/siyuan-note/siyuan/security/advisories/GHSA-2x3p-x74g-442x","title":"Vendor advisory: github.com","kind":"vendor","source":"nvd","publisher":"vendor","text":null,"published_at":"2026-10-22T04:44:47+00:00","relation":"advisory","confidence":null,"note":"Vendor advisory: github.com"},{"id":87565,"url":"https://www.vulncheck.com/advisories/siyuan-before-3.8.9-nil-pointer-dereference-dos-via-mcp-resources-read","title":"Third-party advisory: www.vulncheck.com","kind":"advisory","source":"nvd","publisher":"research","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":"Third-party advisory: www.vulncheck.com"}],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}