CVE-2021-41131 Client metadata path-traversal in python-tuf

What is CVE-2021-41131?

CVE-2021-41131 is a high-severity path traversal vulnerability in theupdateframework python-tuf, published on 19 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

python-tuf is a Python reference implementation of The Update Framework (TUF). In both clients (`tuf/client` and `tuf/ngclient`), there is a path traversal vulnerability that in the worst case can overwrite files ending in `.json` anywhere on the client system on a call to `get_one_valid_targetinfo()`. It occurs because the rolename is used to form the filename, and may contain path traversal characters (ie `../../name.json`). The impact is mitigated by a few facts: It only affects implementations that allow arbitrary rolename selection for delegated targets metadata, The attack requires the ability to A) insert new metadata for the path-traversing role and B) get the role delegated by an existing targets metadata, The written file content is heavily restricted since it needs to be a valid, signed targets file. The file extension is always .json. A fix is available in version 0.19 or newer. There are no workarounds that do not require code changes. Clients can restrict the allowed character set for rolenames, or they can store metadata in files named in a way that is not vulnerable: neither of these approaches is possible without modifying python-tuf.

Weakness: CWE-22

Which versions are affected by CVE-2021-41131?

3 open source packages ship an affected version, including tuf. It affects 1 product.

Products include Linuxfoundation the Update Framework.

How do I fix CVE-2021-41131?

Upgrade tuf to 0.19.0 or later.

Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.

Is CVE-2021-41131 being exploited?

There is no known exploitation of CVE-2021-41131 in the wild and no public exploit code.

Other vulnerabilities in theupdateframework python-tuf

• CVE-2020-6174 Incorrect threshold signature computation in TUF Critical 9.8
• CVE-2020-15163 Invalid root may become trusted root in The Update Framework (TUF) High 8.7
• CVE-2020-6173 Client Denial of Service on TUF Medium 5.3

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-wjw6-2cqr-j4qr, PYSEC-2021-376.