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.
Published: 2026-09-15
Score: 4.9 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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Tracking

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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
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'}


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
  • CWE-918

    Server-Side Request Forgery (SSRF)