{"id":"UBUNTU-CVE-2026-109584","details":"Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a small HPACK-compressed HEADERS block. The block stores one large cookie value in the HPACK dynamic table and then references it tens of thousands of times with 1-byte indexed fields. In the reporter's run, a 49 KB block made a server with default settings allocate a 183 MB cookie binary before any application code ran, and every concurrent stream can repeat the cost. Bandit.HTTP2.Connection caps only the compressed block (max_header_block_size), and its check of the decoded list against max_header_list_size never fires because that setting defaults to :infinity. combine_cookie_crumbs/1 in lib/bandit/http2/stream.ex then joins every crumb into one binary. This issue affects bandit: from 0.3.3 before 1.14.0.","modified":"2026-10-28T20:16:53.365327252Z","published":"2026-10-26T14:16:00Z","upstream":["CVE-2026-109584"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-109584"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-109584"},{"type":"REPORT","url":"https://cna.erlef.org/cves/cve-2026-109584.html"},{"type":"REPORT","url":"https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a"},{"type":"REPORT","url":"https://github.com/mtrudel/bandit/commit/44bf969cd59851622fb6ee4d16227fbc39a77fb4"},{"type":"REPORT","url":"https://github.com/mtrudel/bandit/security/advisories/ghsa-7gfj-7gvq-3xqj"},{"type":"REPORT","url":"https://hex.pm/packages/bandit"},{"type":"REPORT","url":"https://github.com"},{"type":"REPORT","url":"https://github.com/mtrudel/bandit"},{"type":"REPORT","url":"https://repo.hex.pm"},{"type":"REPORT","url":"https://github.com/cveproject/cvelistv5/tree/main/cves/2026/109xxx/cve-2026-109584.json"},{"type":"REPORT","url":"https://nvd.nist.gov/vuln/detail/cve-2026-109584"},{"type":"REPORT","url":"https://osv.dev/vulnerability/eef-cve-2026-109584"}],"affected":[{"package":{"name":"bandit","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/bandit?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.13.2-1","0.13.2-3"],"ecosystem_specific":{"binaries":[{"binary_version":"0.13.2-3","binary_name":"bandit"},{"binary_name":"python-bandit","binary_version":"0.13.2-3"},{"binary_version":"0.13.2-3","binary_name":"python3-bandit"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109584.json"}},{"package":{"name":"bandit","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/bandit?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.0-0ubuntu2"],"ecosystem_specific":{"binaries":[{"binary_version":"1.4.0-0ubuntu2","binary_name":"bandit"},{"binary_name":"python-bandit","binary_version":"1.4.0-0ubuntu2"},{"binary_version":"1.4.0-0ubuntu2","binary_name":"python3-bandit"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109584.json"}},{"package":{"name":"bandit","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/bandit?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.5.1-3","1.6.2-1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.6.2-1","binary_name":"bandit"},{"binary_version":"1.6.2-1","binary_name":"python3-bandit"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109584.json"}},{"package":{"name":"bandit","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/bandit?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.6.2-1"],"ecosystem_specific":{"binaries":[{"binary_name":"bandit","binary_version":"1.6.2-1"},{"binary_version":"1.6.2-1","binary_name":"python3-bandit"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109584.json"}},{"package":{"name":"bandit","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/bandit?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.6.2-3"],"ecosystem_specific":{"binaries":[{"binary_name":"bandit","binary_version":"1.6.2-3"},{"binary_name":"python3-bandit","binary_version":"1.6.2-3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109584.json"}},{"package":{"name":"bandit","ecosystem":"Ubuntu:26.10","purl":"pkg:deb/ubuntu/bandit?arch=source&distro=stonking"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.7.10-3","1.9.4-1"],"ecosystem_specific":{"binaries":[{"binary_name":"bandit","binary_version":"1.9.4-1"},{"binary_name":"python3-bandit","binary_version":"1.9.4-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109584.json"}},{"package":{"name":"bandit","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/bandit?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.7.10-2","1.7.10-3"],"ecosystem_specific":{"binaries":[{"binary_version":"1.7.10-3","binary_name":"bandit"},{"binary_version":"1.7.10-3","binary_name":"python3-bandit"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109584.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"},{"type":"Ubuntu","score":"medium"}]}