CVE-2026-97689: URLLIB3

High severity, CVSS 8.9. EPSS: 0.3% chance of exploitation in the next 30 days.

urllib3 is an HTTP client library for Python. From 1.10.3 until 2.8.0, the HTTPResponse.read_chunked and HTTPResponse.stream methods can allocate unbounded memory because the streaming chunk parser buffers the chunk-size field until newline or EOF without a length bound. The trigger is that a malicious server returns Transfer-Encoding: chunked followed by a very long run of bytes without a newline. The attack mechanism is that a malicious HTTP server sends a very long unterminated chunk-size line. The impact is that unbounded memory allocation can exhaust the client process. This issue is fixed in version 2.8.0.

Affected products

• URLLIB3 URLLIB3: from 1.10.3, before 2.8.0 (fixed in 2.8.0)

Published 2026-09-29. Last modified 2026-09-30.