{"id":"EEF-CVE-2026-58226","summary":"Unauthenticated denial-of-service via unbounded HPACK integer decoding in hpax","details":"## Summary\n\nInefficient Algorithmic Complexity vulnerability in elixir-mint hpax allows unauthenticated denial-of-service via unbounded HPACK integer decoding.\n\nhpax decodes HPACK variable-length integers with no upper bound on the decoded value or the number of continuation octets. 'Elixir.HPAX.Types':decode\\_remaining\\_integer/3 accumulates the integer as int + (value \u003c\u003c\u003c m), shifting by 7 more bits for each continuation octet and stopping only on a terminating octet or truncated input, never because the integer grew too large. Because BEAM integers are arbitrary precision, a run of N continuation octets builds an O(N)-bit bignum and re-adds into an ever-larger bignum on each step, so the total decoding cost is superlinear (about O(N^2)). An unauthenticated attacker who can send an HTTP/2 header block to a server using this decoder (reached through the 'Elixir.HPAX':decode/2 entry point) can supply a small header block that forces a large, attacker-controlled amount of CPU (and transient memory), a denial-of-service amplification.\n\nThis issue affects hpax from 0.1.1 before 1.0.4.","aliases":["CVE-2026-58226","GHSA-jj2p-32j7-whj2"],"modified":"2026-07-30T18:22:03.167317Z","published":"2026-07-06T09:03:47.374Z","database_specific":{"cwe_ids":["CWE-407"],"capec_ids":["CAPEC-130"],"cpe_ids":["cpe:2.3:a:elixir-mint:hpax:*:*:*:*:*:*:*:*"]},"references":[{"type":"ADVISORY","url":"https://github.com/elixir-mint/hpax/security/advisories/GHSA-jj2p-32j7-whj2"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-58226.html"},{"type":"FIX","url":"https://github.com/elixir-mint/hpax/commit/1ba4bb2dc91e80089cf89c73970ac3ded76f17eb"},{"type":"PACKAGE","url":"https://hex.pm/packages/hpax"}],"affected":[{"package":{"name":"hpax","ecosystem":"Hex","purl":"pkg:hex/hpax"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.1.1"},{"fixed":"1.0.4"}]}],"versions":["0.1.1","0.1.2","0.2.0","1.0.0","1.0.1","1.0.2","1.0.3"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-58226.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/elixir-mint/hpax","events":[{"introduced":"56db437a7e2c515e3bdd770ac7947b02cd2390d0"},{"fixed":"1ba4bb2dc91e80089cf89c73970ac3ded76f17eb"}]}],"versions":["v1.0.3","v1.0.2","v1.0.1","v1.0.0","v0.2.0","v0.1.2","v0.1.1"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-58226.json"}}],"schema_version":"1.8.0","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"}],"credits":[{"name":"Peter Ullrich","type":"FINDER"},{"name":"Andrea Leopardi","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen / EEF","type":"ANALYST"},{"name":"Eric Meadows-Jönsson","type":"ANALYST"}]}