Ecosyste.ms: Advisories

Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLTY1NmMtNmN4Zi1odmN2

Deserialization of Untrusted Data in Flask-Caching

Flask-Cache adds easy cache support to Flask. 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.

However, this is not a high-severity issue, as for an attack like this to work, an attacker must:

1. Be able to write arbitrary values to the cache
2. Be able to generate a cache key that will collide with a value being read by the application
3. Cause the application to read a maliciously-injected value

Any situation where all 3 of those is true is a situation where the application has larger problems; for example, if someone's able to inject malicious cached rendered pages into a Flask app's cache, then they can make the website say literally anything they want, regardless of whether it involves the execution of remote code. Basically, the Pickle vulnerability follows from a website already being extremely vulnerable (due to conditions 1 and 2 being met).

Permalink: https://github.com/advisories/GHSA-656c-6cxf-hvcv
JSON: https://advisories.ecosyste.ms/api/v1/advisories/MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLTY1NmMtNmN4Zi1odmN2
Source: GitHub Advisory Database
Origin: Unspecified
Severity: Moderate
Classification: General
Published: almost 3 years ago
Updated: 9 months ago

CVSS Score: 4.2
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:H/A:N

Identifiers: GHSA-656c-6cxf-hvcv, CVE-2021-33026
References:

• https://nvd.nist.gov/vuln/detail/CVE-2021-33026
• https://github.com/sh4nks/flask-caching/pull/209
• https://github.com/pallets-eco/flask-caching/pull/209#issuecomment-1136397937
• https://github.com/advisories/GHSA-656c-6cxf-hvcv
• https://github.com/pypa/advisory-database/tree/main/vulns/flask-caching/PYSEC-2021-13.yaml

Repository: https://github.com/sh4nks/flask-caching
Blast Radius: 13.2

Affected Packages