Improper Handling of Highly Compressed Data (Data Amplification) Affecting urllib3 package, versions [1.22,2.6.3)
Threat Intelligence
This vulnerability is trending on Twitter; this may indicate a growing threat.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PYTHON-URLLIB3-14896210
- published8 Jan 2026
- disclosed7 Jan 2026
- creditUnknown
Introduced: 7 Jan 2026
CVE-2026-21441 (opens in a new tab)How to fix?
Upgrade urllib3 to version 2.6.3 or higher.
Overview
urllib3 is a HTTP library with thread-safe connection pooling, file post, and more.
Affected versions of this package are vulnerable to Improper Handling of Highly Compressed Data (Data Amplification) via the streaming API when handling HTTP redirects. An attacker can cause excessive resource consumption by serving a specially crafted compressed response that triggers decompression of large amounts of data before any read limits are enforced.
Note: This is only exploitable if content is streamed from untrusted sources with redirects enabled.
Workaround
This vulnerability can be mitigated by disabling redirects by setting redirect=False for requests to untrusted sources.