CVE-2026-53956 — rattler_cache
MEDIUMCVE-2026-53956 is a medium-severity (CVSS 5.4) Path Traversal vulnerability in rattler_cache. A fix is available for rattler_cache — see the affected versions and patch details below.
Rattler vulnerable to package cache path traversal via conda package build string
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-53956.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-53956 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
rattler_cache🐍py-rattlerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io, PyPI packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | rattler_cache | all versions | 0.9.0cargo update -p rattler_cache --precise 0.9.0 |
| 🐍PyPI | py-rattler | all versions | 0.24.0pip install --upgrade 'py-rattler==0.24.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rattler_cache, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update rattler_cache to 0.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53956 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.
Frequently Asked Questions
Is CVE-2026-53956 in your dependencies?
Find it across crates.io, PyPI, including transitive dependencies.