# CVE-2026-48737: pyLoad: SSRF guard bypass via IPv6 6to4/NAT64 transition wrappers of internal IPs

> Attackers can bypass SSRF protections in pyLoad using IPv6 transition addresses to access internal networks or cloud metadata.

- **Severity:** Medium 4.9 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Sep 2026
- **Updated:** 16 Sep 2026
- **Also known as:** GHSA-m5x5-28jr-gpjj, PYSEC-2026-2995

## What is CVE-2026-48737?

CVE-2026-48737 is a medium-severity server-side request forgery vulnerability in pyload, published on 15 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-48737?

3 open source packages ship an affected version, including pyload-ng.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `pyload-ng` | PyPI | All versions to 0.5.0b3.dev100 | None |
| `pyload-ng` | PyPI | All versions to 0.5.0b3.dev100 | None |
| `pyload-ng` | PyPI | All versions to 0.5.0b3.dev100 | None |

## How do I fix CVE-2026-48737?

No fix has been published for CVE-2026-48737 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-48737 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48737 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48737 and fix it if it is affected.

What it is: CVE-2026-48737 is a medium-severity server-side request forgery vulnerability in pyload, published on 15 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48737 exists.

Affected packages and fixed versions:
- pyload-ng (PyPI): affected all versions up to 0.5.0b3.dev100; no fix listed
- pyload-ng (PyPI): affected all versions up to 0.5.0b3.dev100; no fix listed
- pyload-ng (PyPI): affected all versions up to 0.5.0b3.dev100; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-48737/ (Markdown: https://insights.sbomify.com/CVE-2026-48737/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48737
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48737
- OSV: https://osv.dev/vulnerability/CVE-2026-48737

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48737/
Summaries are generated and may contain mistakes; the official description above is the record.