{"id":"CVE-2026-48737","summary":"pyLoad: SSRF guard bypass via IPv6 6to4/NAT64 transition wrappers of internal IPs","details":"pyLoad is a free and open-source download manager written in Python. Prior to 0.5.0b3.dev101, is_global_address in src/pyload/core/utils/web/check.py relies on Python's global-address classification without examining IPv4 destinations embedded in 6to4 or NAT64 IPv6 addresses. A low-privileged user can submit an IPv6 literal through parse_urls to the pre-resolution is_global_host guard. Because host_to_ip is pinned to AF_INET, that guard does not evaluate a hostname's AAAA result. Separately, curl resolves hostnames before the pycurl PREREQFUNC in src/pyload/core/network/http/http_request.py applies the same vulnerable is_global_address check to the actual connection address, so a transition-form AAAA result can be permitted even when it terminates at an embedded loopback, private, CGNAT, or link-local IPv4 address. Exploitation requires the pyLoad host to route the applicable transition mechanism, including 6to4 on affected Python 3.9 through 3.11 deployments or NAT64 on a network with a NAT64 gateway. Successful exploitation can enable internal-network reconnaissance, timing-based confirmation, limited service disruption, or cloud metadata disclosure where the wrapped address is routable. This issue is fixed in version 0.5.0b3.dev101.","aliases":["GHSA-m5x5-28jr-gpjj","PYSEC-2026-2995"],"modified":"2026-09-18T03:30:15.709980841Z","published":"2026-09-15T14:40:27.340Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48737.json","unresolved_ranges":[{"extracted_events":[{"fixed":"0.5.0b3.dev101"}],"source":"AFFECTED_FIELD"},{"extracted_events":[{"introduced":"3.9"},{"fixed":"3.11"}],"source":"DESCRIPTION"}],"cna_assigner":"GitHub_M","cwe_ids":["CWE-918"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48737.json"},{"type":"ADVISORY","url":"https://github.com/pyload/pyload/security/advisories/GHSA-m5x5-28jr-gpjj"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-48737"},{"type":"FIX","url":"https://github.com/pyload/pyload/commit/ba7491046b2d430732be490913e4cbf1f1e899c2"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/pyload/pyload","events":[{"introduced":"0"},{"fixed":"ba7491046b2d430732be490913e4cbf1f1e899c2"}],"database_specific":{"source":"REFERENCES"}}],"versions":["v0.4.9","v0.4.8","v0.4.7","v0.4.6","v0.4.5","v0.4.4","v0.4.3","v0.4.2","v0.4.1","v0.4","v0.3.2","v0.3.1","v0.3","v0.2.2","v0.2.1","v0.2","v0.1.1","v0.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-48737.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:L"}]}