Critical severity9.8NVD Advisory· Published May 13, 2021· Updated Jun 17, 2026
CVE-2021-33026
CVE-2021-33026
Description
The Flask-Caching extension through 1.10.1 for Flask relies on Pickle for serialization, which may lead to remote code execution or local privilege escalation. If an attacker gains access to cache storage (e.g., filesystem, Memcached, Redis, etc.), they can construct a crafted payload, poison the cache, and execute Python code. NOTE: a third party indicates that exploitation is extremely unlikely unless the machine is already compromised; in other cases, the attacker would be unable to write their payload to the cache and generate the required collision
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Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
Flask-CachingPyPI | <= 1.10.1 | — |
Affected products
3- Flask/Flask-Cachingdescription
- cpe:2.3:a:flask-caching_project:flask-caching:*:*:*:*:*:flask:*:*Range: <=1.10.1
Patches
Vulnerability mechanics
References
5- github.com/pallets-eco/flask-caching/pull/209nvdIssue TrackingPatchThird Party AdvisoryWEB
- github.com/sh4nks/flask-caching/pull/209nvdPatchThird Party AdvisoryWEB
- github.com/advisories/GHSA-656c-6cxf-hvcvghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2021-33026ghsaADVISORY
- github.com/pypa/advisory-database/tree/main/vulns/flask-caching/PYSEC-2021-13.yamlghsaWEB
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