{"id":"CVE-2026-7790","aliases":["EEF-CVE-2026-7790","GHSA-32p9-57cr-4x65"],"url":"https://o3.security/vulnerability/CVE-2026-7790","summary":"Unbounded chunk-size hex digits in cowlib cause quadratic CPU and memory DoS","details":"Uncontrolled Resource Consumption vulnerability in ninenines cowlib (cow_http_te module) allows Excessive Allocation.\n\nThe chunked transfer-encoding parser in cow_http_te accepts an unbounded number of hex digits in the chunk-size field. Each digit causes a bignum multiplication (Len * 16 + digit), so parsing N hex digits requires O(N²) CPU work and O(N) memory. Additionally, when input is drip-fed, the parser discards the accumulated length on each partial read and restarts from zero on resumption, raising the cost to O(N³). An unauthenticated remote attacker can exploit this by sending an HTTP/1.1 request with Transfer-Encoding: chunked and a very long chunk-size hex string to cause denial of service through CPU exhaustion and memory amplification.\n\nThis vulnerability is associated with program file src/cow_http_te.erl and program routines cow_http_te:stream_chunked/2, cow_http_te:chunked_len/4.\n\nThis issue affects cowlib: from 0.6.0 before 2.16.1.","published":"2026-05-11T18:06:41.490Z","modified":"2026-08-07T11:51:07.822368891Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Hex","name":"cowlib","fixedVersion":"2.16.1"}],"fix":{"url":"https://github.com/ninenines/cowlib/commit/a4b8039ce8c93ab00867ef6b7e888822c09f4369","label":"ninenines/cowlib@a4b8039"},"references":[{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-7790"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://cna.erlef.org/cves/CVE-2026-7790.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/7xxx/CVE-2026-7790.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-7790"},{"type":"FIX","url":"https://github.com/ninenines/cowlib/commit/a4b8039ce8c93ab00867ef6b7e888822c09f4369"},{"type":"PACKAGE","url":"https://github.com/ninenines/cowlib"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-07T11:51:07.822368891Z"}}