{"id":"CVE-2026-74905","state":"PUBLISHED","title":"SiYuan before v3.7.4 SSRF via IPv6 Transition Address Bypass","description":"SiYuan before v3.7.4 contains a server-side request forgery (SSRF) vulnerability in the isPrivateIP function in kernel/util/net.go, used by SSRFSafeDialer to enforce SSRF protection in SafeMode. The function only checks for loopback, link-local unicast, private, and unspecified addresses and does not recognize IPv6 transition addresses (NAT64 64:ff9b::/96, 6to4 2002::/16, Teredo 2001::/32) that embed private IPv4 destinations. When SafeMode is enabled, an authenticated attacker can bypass the SSRF guard via the network forward proxy, WebSocket proxy, or SSE proxy endpoints by supplying a URL whose hostname resolves to such a transition address, reaching internal services and cloud metadata endpoints (e.g., 169.254.169.254). Because the forward proxy returns the full response body, this is a full-read SSRF that can be used to steal instance credentials, reach internal services, and port-scan internal infrastructure.","publishedAt":"2026-08-18T11:19:36.761Z","updatedAt":"2026-08-19T14:10:27.258Z","severity":{"score":6.9,"label":"Medium","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L","source":"VulnCheck"},"assigner":"VulnCheck","products":["siyuan-note siyuan"],"affected":[{"vendor":"siyuan-note","product":"siyuan","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"3.7.4","versionType":"semver"},{"version":"3.7.4","status":"unaffected","versionType":"semver"}]}],"references":["https://github.com/siyuan-note/siyuan/security/advisories/GHSA-qq8m-8p8v-x4xg","https://www.vulncheck.com/advisories/siyuan-before-ssrf-via-ipv6-transition-address-bypass"],"weaknesses":["CWE-918"],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74905.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74905","state":"PUBLISHED","datePublished":"2026-08-18T11:19:36.761Z","dateUpdated":"2026-08-19T14:10:27.258Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-08-17T10:48:45.738Z"},"containers":{"cna":{"title":"SiYuan before v3.7.4 SSRF via IPv6 Transition Address Bypass","descriptions":[{"lang":"en","value":"SiYuan before v3.7.4 contains a server-side request forgery (SSRF) vulnerability in the isPrivateIP function in kernel/util/net.go, used by SSRFSafeDialer to enforce SSRF protection in SafeMode. The function only checks for loopback, link-local unicast, private, and unspecified addresses and does not recognize IPv6 transition addresses (NAT64 64:ff9b::/96, 6to4 2002::/16, Teredo 2001::/32) that embed private IPv4 destinations. When SafeMode is enabled, an authenticated attacker can bypass the SSRF guard via the network forward proxy, WebSocket proxy, or SSE proxy endpoints by supplying a URL whose hostname resolves to such a transition address, reaching internal services and cloud metadata endpoints (e.g., 169.254.169.254). Because the forward proxy returns the full response body, this is a full-read SSRF that can be used to steal instance credentials, reach internal services, and port-scan internal infrastructure."}],"affected":[{"vendor":"siyuan-note","product":"siyuan","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"3.7.4","versionType":"semver"},{"version":"3.7.4","status":"unaffected","versionType":"semver"}]}],"references":[{"url":"https://github.com/siyuan-note/siyuan/security/advisories/GHSA-qq8m-8p8v-x4xg","tags":["vendor-advisory"],"name":"GitHub Security Advisory (GHSA-qq8m-8p8v-x4xg)"},{"url":"https://www.vulncheck.com/advisories/siyuan-before-ssrf-via-ipv6-transition-address-bypass","name":"VulnCheck Advisory: SiYuan before v3.7.4 SSRF via IPv6 Transition Address Bypass","tags":["third-party-advisory"]}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":6.9,"baseSeverity":"MEDIUM","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"LOW","subConfidentialityImpact":"LOW","subIntegrityImpact":"LOW","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS"},{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.1,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"LOW","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N","version":"3.1"},"format":"CVSS"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-918","lang":"en","description":"Server-Side Request Forgery (SSRF)","type":"CWE"}]}],"providerMetadata":{"shortName":"VulnCheck","orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateUpdated":"2026-08-18T11:19:36.761Z"},"datePublic":"2026-08-04T00:00:00.000Z","cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:b3log:siyuan:*:*:*:*:*:*:*:*","versionEndExcluding":"3.7.4"}]}]}],"x_generator":{"engine":"vulncheck-endgame"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/siyuan-note/siyuan/security/advisories/GHSA-qq8m-8p8v-x4xg","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-19T14:09:42.098446Z","id":"CVE-2026-74905","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-19T14:10:27.258Z"}}]}}}