{"id":"CVE-2026-84378","title":"HTTPX2 is a next generation HTTP client for Python","summary":"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-contr…","severity":"medium","cvss":5.9,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-407","CWE-606"],"vendor":"httpx2","product":"httpx2","affected":["httpx2 >= 2.5.0, < 2.10.0"],"patched":["httpx2 2.10.0"],"published":"2026-09-02","updated":"2026-09-09","sourceUpdated":"2026-09-09T21:05:23.237","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-84378","references":[{"url":"https://github.com/pydantic/httpx2/commit/cbfc0e04ef6507da29ccbb3b9c2e5b23dd693414","label":"security-advisories@github.com"},{"url":"https://github.com/pydantic/httpx2/pull/1071","label":"security-advisories@github.com"},{"url":"https://github.com/pydantic/httpx2/pull/1117","label":"security-advisories@github.com"},{"url":"https://github.com/pydantic/httpx2/releases/tag/v2.10.0","label":"security-advisories@github.com"},{"url":"https://github.com/pydantic/httpx2/security/advisories/GHSA-f2fp-rgf2-35cp","label":"security-advisories@github.com"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-84378"},{"url":"https://github.com/pydantic/httpx2"},{"url":"https://github.com/advisories/GHSA-f2fp-rgf2-35cp"},{"url":"https://pypi.org/project/httpx2"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-84378.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-84378"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2527694"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-84378"}],"tags":["nvd","osv","pip","ghsa","csaf","vex","red-hat"],"epss":0.0032,"epssPercentile":0.25154,"aliases":["GHSA-f2fp-rgf2-35cp","PYSEC-2026-3847"],"ecosystem":"pip","ingestedAt":"2026-09-08T21:11:12.322Z","slug":"CVE-2026-84378","body":"## Overview\n\nHTTPX2 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-84378)\n\nAffected packages:\n\n- `httpx2 >= 2.5.0, < 2.10.0`\n\nPatched in:\n\n- `httpx2 2.10.0`\n\nSource: https://osv.dev/vulnerability/GHSA-f2fp-rgf2-35cp\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Lightspeed Core, Red Hat OpenShift AI (RHOAI) · no fix planned: Lightspeed Core, Red Hat OpenShift AI (RHOAI) · updated 2026-09-22 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-84378.json)","depth":"sunlit","depthScore":33,"depthScoreParts":{"impact":32.5,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}