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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-48737
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-15 15:17:16 UTC
Updated2026-09-16 17:17:18 UTC
DescriptionpyLoad 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.

Risk And Classification

Primary CVSS: v3.1 4.9 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:L

EPSS: 0.001810000 probability, percentile 0.079330000 (date 2026-09-16)

Problem Types: CWE-918 | CWE-918 CWE-918: Server-Side Request Forgery (SSRF)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary4.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:L
3.1CNADECLARED4.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
None
Availability
Low

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:L

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Pyload Pyload affected < 0.5.0b3.dev101 Not specified

References

ReferenceSourceLinkTags
github.com/pyload/pyload/security/advisories/GHSA-m5x5-28jr-gpjj 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/pyload/pyload/commit/ba7491046b2d430732be490913e4cbf1f1e899c2 [email protected] github.com
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