{"id":"CVE-2026-49755","aliases":["EEF-CVE-2026-49755","GHSA-655f-mp8p-96gv"],"url":"https://o3.security/vulnerability/CVE-2026-49755","summary":"Decompression bomb DoS in Req via auto-decoded archive and compressed response bodies","details":"Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in wojtekmach Req allows attacker-controlled HTTP servers to exhaust memory in a Req client via decompression-bomb response bodies.\n\nReq's default response pipeline includes Req.Steps.decode_body/1 and Req.Steps.decompress_body/1 in lib/req/steps.ex. decode_body/1 dispatches on the server-supplied content-type (or URL extension) and calls :zip.extract(body, [:memory]) for application/zip, :erl_tar.extract({:binary, body}, [:memory]) for application/x-tar, and :erl_tar.extract({:binary, body}, [:memory, :compressed]) for application/gzip / .tgz. Each returns the full decompressed archive contents as a [{name, bytes}] list in memory, with no per-entry or total size cap. decompress_body/1 walks the content-encoding header and chains :zlib/:brotli/:ezstd decoders, so a response advertising content-encoding: gzip, gzip, gzip inflates through multiple layers without bound.\n\nBoth steps are enabled by default, no caller opt-in is required, and the attacker controls the content-type and content-encoding headers on their own server (or on any host reached via Req's automatic redirect following). A sub-megabyte response can expand to multiple gigabytes on the victim, crashing the BEAM process.\n\nThis issue affects req: from 0.1.0 before 0.6.1.","published":"2026-06-08T15:20:57.415Z","modified":"2026-08-12T03:51:44.637633399Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Hex","name":"req","fixedVersion":"0.6.1"}],"fix":{"url":"https://github.com/wojtekmach/req/commit/84977e5b1a83f26e749d55ad06e3625464af4e8d","label":"wojtekmach/req@84977e5"},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-49755.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-49755"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/49xxx/CVE-2026-49755.json"},{"type":"ADVISORY","url":"https://github.com/wojtekmach/req/security/advisories/GHSA-655f-mp8p-96gv"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49755"},{"type":"FIX","url":"https://github.com/wojtekmach/req/commit/84977e5b1a83f26e749d55ad06e3625464af4e8d"},{"type":"PACKAGE","url":"https://github.com/wojtekmach/req"},{"type":"PACKAGE","url":"https://github.com/wojtekmach/req.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:44.637633399Z"}}