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Fencer Vulns
medium 4.9

CVE-2026-48737 json

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

published 2026-07-09 4 mo ago modified 2026-09-16 53 d ago also EUVD-2026-78593 , GHSA-m5x5-28jr-gpjj , PYSEC-2026-2995

cvss
4.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 21%
public exploits
0
none known

Summary

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.

Patch / fix

  • pyload-ng_project pyload-ng 0.5.0b3.dev101
  • pyload pyload 0.5.0b3.dev101

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
53 d ago

Exploit prediction

0.29% chance of exploitation in the next 30 days, higher than 21% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/pyload/pyload/security/advisories/GHSA-m5x5-28jr-gpjj referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 4.9 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:L
GitHub 3.1 4.9 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:L
OSV 3.1 4.9 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:L

Affected packages

ecosystem package affected fixed in
pypi pyload-ng
<=0.5.0b3.dev100
 no fix listed

Affected products

  • pyload pyload

Classification

Weakness
  • CWE-918 Server-Side Request Forgery

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.