{"cve":"CVE-2026-97688","nvd":{"published":"2026-09-29T16:17:18.680","modified":"2026-10-13T20:21:30.583","status":"Analyzed","description":"urllib3 is an HTTP client library for Python. From 2.6.2 until 2.8.0, HTTPResponse.stream and HTTPResponse.read_chunked can enter an infinite loop because the Deflate decoder retains trailing bytes as unconsumed input after reaching end-of-stream and repeatedly decodes them without progress. The issue occurs when an untrusted server sends a chunked Deflate response whose decoded body exceeds a positive finite chunk size and whose encoded body has trailing bytes, specifically a response with Transfer-Encoding: chunked and Content-Encoding: deflate, content decoding enabled, and the positive finite amt=N streaming chunk size. The attack mechanism is that a malicious server returns a compressed chunked response with trailing bytes after the Deflate stream. The impact is excessive CPU usage and a request that does not complete, and network read timeouts do not interrupt the loop because no further socket read occurs. This issue is fixed in version 2.8.0.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N","score":6.9},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","score":5.3},"cwes":["CWE-835"],"references":["https://github.com/urllib3/urllib3/commit/ea2ad7b21a80da3632f80016526a18864586077f","https://github.com/urllib3/urllib3/releases/tag/2.8.0","https://github.com/urllib3/urllib3/security/advisories/GHSA-gh4c-6fx4-qh6g"],"products":["python:urllib3"],"source":"nvd","synced_at":"2026-10-19T22:56:48.555445741+00:00"},"epss":{"cve":"CVE-2026-97688","score":0.00292,"percentile":0.21527,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-gh4c-6fx4-qh6g","url":"https://osv.dev/vulnerability/GHSA-gh4c-6fx4-qh6g","summary":"urllib3: Chunked Deflate streaming can enter an infinite loop","modified":"2026-10-01T17:55:40.608255720Z","packages":[{"ecosystem":"PyPI","name":"urllib3","purl":"pkg:pypi/urllib3","ranges":[">=2.6.2 <2.8.0"],"fixed":["2.8.0"]}]},{"id":"PYSEC-2026-4176","url":"https://osv.dev/vulnerability/PYSEC-2026-4176","summary":"urllib3: Chunked Deflate streaming can enter an infinite loop","modified":"2026-10-01T17:45:18.545924093Z","packages":[{"ecosystem":"PyPI","name":"urllib3","purl":"pkg:pypi/urllib3","ranges":[">=2.6.2 <2.8.0"],"fixed":["2.8.0"]}]}],"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."]}