PatchTheCVECVE-2021-33026: The Flask-Caching extension through 1.10.1 for Flask relies on Pickle for serialization, which may lead to rem
CVE-2021-33026 is a critical-severity flaw (CVSS 9.8) affecting flask-caching. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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 othe
Why this priority
- Critical severity
- EPSS top 6%: very likely to be exploited
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 7.3% (top 6%) |
| CISA exploited list | No |
| Weakness | CWE-502 |
| Published | 2021-05-13 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-33026?
flask-caching: upgrade to newer than 1.10.1. Exact commands for each OS are on this page.
Is CVE-2021-33026 being exploited?
CVE-2021-33026 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-33026 affect?
CVE-2021-33026 affects flask-caching. Severity is critical (CVSS 9.8). 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
How urgent is CVE-2021-33026?
Priority 63/100. Critical severity; EPSS top 6%: very likely to be exploited; Remotely exploitable, no login, no user action
Software pages
Python vulnerabilities · Redis vulnerabilities · Memcached vulnerabilities · Flask vulnerabilities