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.
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-m5x5-28jr-gpjj pyLoad: SSRF guard bypass via IPv6 6to4/NAT64 transition wrappers of internal IPs
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Tue, 15 Sep 2026 16:15:00 +0000

Type Values Removed Values Added
First Time appeared Pyload
Pyload pyload
Vendors & Products Pyload
Pyload pyload

Tue, 15 Sep 2026 14:45:00 +0000

Type Values Removed Values Added
Description 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.
Title pyLoad: SSRF guard bypass via IPv6 6to4/NAT64 transition wrappers of internal IPs
Weaknesses CWE-918
References
Metrics cvssV3_1

{'score': 4.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:L'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-15T14:40:27.340Z

Reserved: 2026-05-22T19:10:35.746Z

Link: CVE-2026-48737

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-15T15:17:16.220

Modified: 2026-09-15T15:17:16.220

Link: CVE-2026-48737

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-15T16:00:16Z

Weaknesses