{"cve":"CVE-2021-33026","nvd":{"published":"2021-05-13T23:15:07.367","modified":"2026-06-17T03:54:02.267","status":"Modified","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","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8},"cwes":["CWE-502"],"references":["https://github.com/pallets-eco/flask-caching/pull/209#issuecomment-1136397937","https://github.com/sh4nks/flask-caching/pull/209","https://github.com/pallets-eco/flask-caching/pull/209#issuecomment-1136397937","https://github.com/sh4nks/flask-caching/pull/209"],"products":["flask-caching_project:flask-caching"],"source":"nvd","synced_at":"2026-10-19T21:18:09.669877188+00:00"},"epss":{"cve":"CVE-2021-33026","score":0.07348,"percentile":0.944,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-656c-6cxf-hvcv","url":"https://osv.dev/vulnerability/GHSA-656c-6cxf-hvcv","summary":"Deserialization of Untrusted Data in Flask-Caching","modified":"2024-02-16T08:16:33.120862Z","packages":[{"ecosystem":"PyPI","name":"flask-caching","purl":"pkg:pypi/flask-caching","ranges":["<=1.10.1"],"fixed":[]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}