{"id":"UBUNTU-CVE-2026-8466","details":"Allocation of Resources Without Limits or Throttling vulnerability in ninenines cowboy allows denial of service via unbounded buffer accumulation in multipart header parsing. cowboy_req:read_part/3 in src/cowboy_req.erl accumulates incoming request bytes into a Buffer binary with no upper-bound check. When cow_multipart:parse_headers/2 returns more or {more, Buffer2}, the function reads up to Length bytes (default 64 KB) from the request body and recurses with the enlarged buffer. There is no equivalent of the byte_size(Acc) \u003e Length guard present in the sibling function read_part_body/4. An unauthenticated attacker can send a multipart/form-data request whose body never yields a complete header section — for example, a body that never contains the advertised boundary delimiter, or one whose header lines never contain \\r\\n\\r\\n — and force the server process to accumulate memory linearly with the bytes the protocol layer is willing to deliver. A handful of concurrent such uploads is sufficient to exhaust BEAM memory. This issue affects cowboy from 2.0.0 before 2.15.0.","modified":"2026-05-20T22:03:08.537922024Z","published":"2026-05-13T19:17:00Z","upstream":["CVE-2026-8466"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-8466"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-8466"},{"type":"REPORT","url":"https://cna.erlef.org/cves/CVE-2026-8466.html"},{"type":"REPORT","url":"https://osv.dev/vulnerability/EEF-CVE-2026-8466"},{"type":"REPORT","url":"https://github.com/ninenines/cowboy/commit/5c6a2061b41bb5771c4659fac7d5a822dca5bafb"}],"affected":[{"package":{"name":"erlang-cowboy","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/erlang-cowboy?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.0~pre.1+dfsg1-1"],"ecosystem_specific":{"binaries":[{"binary_name":"erlang-cowboy","binary_version":"2.0.0~pre.1+dfsg1-1"},{"binary_name":"erlang-cowboy-examples","binary_version":"2.0.0~pre.1+dfsg1-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-8466.json"}},{"package":{"name":"erlang-cowboy","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/erlang-cowboy?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.0~pre.1+dfsg1-2"],"ecosystem_specific":{"binaries":[{"binary_version":"2.0.0~pre.1+dfsg1-2","binary_name":"erlang-cowboy"},{"binary_version":"2.0.0~pre.1+dfsg1-2","binary_name":"erlang-cowboy-examples"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-8466.json"}},{"package":{"name":"erlang-cowboy","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/erlang-cowboy?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.0~pre.1+dfsg1-4"],"ecosystem_specific":{"binaries":[{"binary_name":"erlang-cowboy","binary_version":"2.0.0~pre.1+dfsg1-4"},{"binary_name":"erlang-cowboy-examples","binary_version":"2.0.0~pre.1+dfsg1-4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-8466.json"}},{"package":{"name":"erlang-cowboy","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/erlang-cowboy?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.0~pre.1+dfsg1-4"],"ecosystem_specific":{"binaries":[{"binary_version":"2.0.0~pre.1+dfsg1-4","binary_name":"erlang-cowboy"},{"binary_version":"2.0.0~pre.1+dfsg1-4","binary_name":"erlang-cowboy-examples"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-8466.json"}},{"package":{"name":"erlang-cowboy","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/erlang-cowboy?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.0~pre.1+dfsg1-4"],"ecosystem_specific":{"binaries":[{"binary_version":"2.0.0~pre.1+dfsg1-4","binary_name":"erlang-cowboy"},{"binary_name":"erlang-cowboy-examples","binary_version":"2.0.0~pre.1+dfsg1-4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-8466.json"}},{"package":{"name":"erlang-cowboy","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/erlang-cowboy?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.0~pre.1+dfsg1-4"],"ecosystem_specific":{"binaries":[{"binary_name":"erlang-cowboy","binary_version":"2.0.0~pre.1+dfsg1-4"},{"binary_name":"erlang-cowboy-examples","binary_version":"2.0.0~pre.1+dfsg1-4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-8466.json"}},{"package":{"name":"erlang-cowboy","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/erlang-cowboy?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.0~pre.1+dfsg1-4","2.0.0~pre.1+dfsg1-4build1"],"ecosystem_specific":{"binaries":[{"binary_version":"2.0.0~pre.1+dfsg1-4build1","binary_name":"erlang-cowboy"},{"binary_name":"erlang-cowboy-examples","binary_version":"2.0.0~pre.1+dfsg1-4build1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-8466.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"},{"type":"Ubuntu","score":"medium"}]}