{"cve":"CVE-2026-84378","nvd":{"published":"2026-09-02T18:21:29.153","modified":"2026-09-09T21:05:23.237","status":"Awaiting Analysis","description":"HTTPX2 is a next generation HTTP client for Python. From 2.5.0 until 2.10.0, the HTTPX2 Server-Sent Events parser in src/httpx2/httpx2/_sse.py repeatedly copies and rescans buffered text in _SSELineDecoder.decode() when an attacker-controlled or compromised SSE endpoint splits one unterminated line across many response chunks. The behavior affects httpx2.Client.sse() and httpx2.AsyncClient.sse(), and the total processing work grows quadratically with the line length, allowing a crafted stream to consume excessive CPU and block a synchronous worker or asynchronous event loop. This issue is fixed in version 2.10.0.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","score":5.9},"cwes":["CWE-407"],"references":["https://github.com/pydantic/httpx2/commit/cbfc0e04ef6507da29ccbb3b9c2e5b23dd693414","https://github.com/pydantic/httpx2/pull/1071","https://github.com/pydantic/httpx2/pull/1117","https://github.com/pydantic/httpx2/releases/tag/v2.10.0","https://github.com/pydantic/httpx2/security/advisories/GHSA-f2fp-rgf2-35cp"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:50:50.842544443+00:00"},"epss":{"cve":"CVE-2026-84378","score":0.00315,"percentile":0.24496,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-f2fp-rgf2-35cp","url":"https://osv.dev/vulnerability/GHSA-f2fp-rgf2-35cp","summary":"HTTPX2: Quadratic SSE line buffering can cause CPU denial of service","modified":"2026-09-10T12:26:01.695645755Z","packages":[{"ecosystem":"PyPI","name":"httpx2","purl":"pkg:pypi/httpx2","ranges":[">=2.5.0 <2.10.0"],"fixed":["2.10.0"]}]},{"id":"PYSEC-2026-3847","url":"https://osv.dev/vulnerability/PYSEC-2026-3847","summary":"HTTPX2: Quadratic SSE line buffering can cause CPU denial of service","modified":"2026-09-10T12:15:05.087047573Z","packages":[{"ecosystem":"PyPI","name":"httpx2","purl":"pkg:pypi/httpx2","ranges":[">=2.5.0 <2.10.0"],"fixed":["2.10.0"]}]}],"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."]}