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pyLoad: SSRF guard bypass via IPv6 6to4/NAT64 transition wrappers of internal IPs

CVSS 3.1 4.9 MEDIUMCheck source for fixed versionsKEV status unknown

cve-program · CVE-2026-48737

Published

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.

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Affected versions, risk and source history

cve-program · CVE-2026-48737

Published

pyload

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "pyload",
                    "product": "pyload",
                    "versions": [
                        {
                            "version": "< 0.5.0b3.dev101",
                            "status": "affected"
                        }
                    ]
                }

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Sources read 13 Nov 11:05 UTC · 270 of 275 readable · 268 fully read · documentation 469/469 current