{"id":"UBUNTU-CVE-2026-71554","details":"h2 is a pure-Python implementation of a HTTP/2 protocol stack. Versions up to and including 4.4.0 accept request header blocks containing more than one Host header, and forward every Host header to the consuming application. Where the consumer downgrades HTTP/2 to HTTP/1.1, the resulting request carries two Host header lines, providing a request smuggling primitive. This issue is fixed in version 4.4.1.","modified":"2026-08-13T00:14:08Z","published":"2026-08-06T22:18:00Z","upstream":["CVE-2026-71554"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-71554"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-71554"},{"type":"REPORT","url":"https://github.com/python-hyper/h2/security/advisories/GHSA-6hr6-w5qg-qmwg"},{"type":"REPORT","url":"https://github.com/python-hyper/h2/commit/292a40829feefda98c8509dcdbbb4a57af9bd6a6"}],"affected":[{"package":{"name":"python-h2","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/python-h2?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.1-1","3.0.1-2","3.0.1-3"],"ecosystem_specific":{"binaries":[{"binary_name":"python-h2","binary_version":"3.0.1-3"},{"binary_version":"3.0.1-3","binary_name":"python3-h2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71554.json"}},{"package":{"name":"python-h2","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/python-h2?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.1-4","3.0.1-4.1ubuntu1","3.0.1-5","3.1.1-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-h2","binary_version":"3.1.1-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71554.json"}},{"package":{"name":"python-h2","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/python-h2?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.0.0-3","4.1.0-3ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-h2","binary_version":"4.1.0-3ubuntu1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71554.json"}},{"package":{"name":"python-h2","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/python-h2?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.1.0-4"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-h2","binary_version":"4.1.0-4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71554.json"}},{"package":{"name":"python-h2","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/python-h2?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.2.0-1","4.3.0-1"],"ecosystem_specific":{"binaries":[{"binary_version":"4.3.0-1","binary_name":"python3-h2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71554.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},{"type":"Ubuntu","score":"medium"}]}