CVE-2026-53956 Rattler vulnerable to package cache path traversal via conda package build string
Attacker can write files outside cache directory via malicious conda channel metadata, potentially leading to code execution.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-53956?
CVE-2026-53956 is a medium-severity path traversal vulnerability in conda py-rattler, published on 9 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Rattler is a library that provides common functionality used within the conda ecosystem. `rattler_cache` prior to version 0.9.0 and `py-rattler` prior to version 0.24.0 were vulnerable to package-cache path traversal when handling package metadata from conda channels. During cache materialization, the `ratter_cache` code used the package record `build` string as part of a cache key that was joined into a filesystem path. A malicious or untrusted channel could publish repodata with path separators or traversal components in that field, causing package contents to be written outside the configured package cache directory. The issue requires use of a malicious or otherwise untrusted conda channel. Curated channels that validate package metadata are not expected to allow malformed build strings of this form. Users should upgrade to `rattler_cache` version 0.9.0 or `py-rattler` version 0.24.0 and avoid untrusted conda channels.
Which versions are affected by CVE-2026-53956?
5 open source packages ship an affected version, including py-rattler, py_rattler and rattler_cache.
| Package | Affected | Fixed in |
|---|---|---|
py-rattler PyPI | All versions | 0.24.0 |
py-rattler PyPI | All versions | 0.24.0 |
py_rattler PyPI | All versions | 0.24.0 |
rattler_cache crates.io | All versions | 0.9.0 |
rattler_cache crates.io | All versions | 0.9.0 |
How do I fix CVE-2026-53956?
Upgrade py-rattler to 0.24.0 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-53956 being exploited?
There is no known exploitation of CVE-2026-53956 in the wild and no public exploit code.
Sources
Also known as GHSA-h672-p7h7-97v9, PYSEC-2026-2970.