{"id":"CVE-2026-97688","summary":"urllib3: Chunked Deflate streaming can enter an infinite loop","details":"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.","aliases":["GHSA-gh4c-6fx4-qh6g"],"modified":"2026-09-30T03:50:16.965257255Z","published":"2026-09-29T15:32:17.622Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/97xxx/CVE-2026-97688.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-835"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/97xxx/CVE-2026-97688.json"},{"type":"FIX","url":"https://github.com/urllib3/urllib3/commit/ea2ad7b21a80da3632f80016526a18864586077f"},{"type":"WEB","url":"https://github.com/urllib3/urllib3/releases/tag/2.8.0"},{"type":"ADVISORY","url":"https://github.com/urllib3/urllib3/security/advisories/GHSA-gh4c-6fx4-qh6g"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-97688"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/urllib3/urllib3","events":[{"introduced":"83f8643ffb5b7f197457379148e2fa118ab0fcdc"},{"fixed":"b1d30ab61fe0db8f11092805e8c5ac43e091064a"}],"database_specific":{"extracted_events":[{"introduced":"2.6.2"},{"fixed":"2.8.0"}],"source":"AFFECTED_FIELD"}}],"versions":["2.7.0","2.6.3","2.6.2"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-97688.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}