{"id":"CVE-2026-66731","aliases":["EUVD-2026-49360","GHSA-vg6c-748h-g68q"],"status":"published","title":"facil.io 0.7.5 - 0.7.6 HTTP/1.1 Chunked Transfer Encoding Parser Crash DoS","description":"facil.io 0.7.5 through 0.7.6 contains a denial-of-service vulnerability in the HTTP/1.1 chunked transfer encoding parser that allows unauthenticated remote attackers to crash the server by sending a negative chunk size value. Attackers can send a single POST request with a Transfer-Encoding: chunked header containing a leading minus sign in the chunk size field, causing the parser in http1_parser.h to compute a large positive integer from the negated value, corrupting internal state and moving the read pointer into unmapped memory resulting in a fault.","severity":{"version":"4.0","score":8.7,"vector":"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","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00784,"percentile":0.56321,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":true,"fix_available":false},"cwes":["CWE-125"],"published":"2026-07-27T16:57:01Z","modified":"2026-10-28T02:30:33Z","exploits":[{"source":"pocgithub","id":"theopaid/CVE-2026-66731-Negative-Chunk-Size-Parsing-Causes-Memory-Corruption-leading-to-Server-Crash","title":"theopaid/CVE-2026-66731-Negative-Chunk-Size-Parsing-Causes-Memory-Corruption-leading-to-Server-Crash","date":"2026-07-24","url":"https://github.com/theopaid/CVE-2026-66731-Negative-Chunk-Size-Parsing-Causes-Memory-Corruption-leading-to-Server-Crash"}],"products":[{"vendor":"boazsegev","product":"facil.io"}],"references":[{"url":"https://tpaidakis.com/writeups/facilio-parser-dos/","tags":["technical-description","exploit","evidence"]},{"url":"https://github.com/theopaid/Negative-Chunk-Size-Parsing-Causes-Memory-Corruption-in-facil.io-leading-to-Server-Crash","tags":["technical-description","exploit","evidence"]},{"url":"https://www.vulncheck.com/advisories/facil-io-http-chunked-transfer-encoding-parser-crash-dos","tags":["third-party-advisory","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66731","tags":["advisory"]},{"url":"https://tpaidakis.com/writeups/facilio-parser-dos"},{"url":"https://github.com/advisories/GHSA-vg6c-748h-g68q"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66731.json","tags":["advisory"]},{"url":"https://github.com/boazsegev/facil.io","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-66731","title":"facil.io 0.7.5 - 0.7.6 HTTP/1.1 Chunked Transfer Encoding Parser Crash DoS","description":"facil.io 0.7.5 through 0.7.6 contains a denial-of-service vulnerability in the HTTP/1.1 chunked transfer encoding parser that allows unauthenticated remote attackers to crash the server by sending a negative chunk size value. Attackers can send a single POST request with a Transfer-Encoding: chunked header containing a leading minus sign in the chunk size field, causing the parser in http1_parser.h to compute a large positive integer from the negated value, corrupting internal state and moving the read pointer into unmapped memory resulting in a fault.","status":"published","published":"2026-07-27T16:57:01.077Z","modified":"2026-07-31T18:20:09.6Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high","assessor":"cna"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-125"],"updated_at":"2026-11-02T14:20:12.939084Z"}],"euvd":[{"id":"EUVD-2026-49360","description":"facil.io 0.7.5 through 0.7.6 contains a denial-of-service vulnerability in the HTTP/1.1 chunked transfer encoding parser that allows unauthenticated remote attackers to crash the server by sending a negative chunk size value. Attackers can send a single POST request with a Transfer-Encoding: chunked header containing a leading minus sign in the chunk size field, causing the parser in http1_parser.h to compute a large positive integer from the negated value, corrupting internal state and moving the read pointer into unmapped memory resulting in a fault.","status":"published","published":"2026-07-27T16:57:01Z","modified":"2026-07-31T18:20:09Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"updated_at":"2026-11-02T18:02:25.522444Z"}],"ghsa":[{"id":"GHSA-vg6c-748h-g68q","title":"facil.io 0.7.5 through 0.7.6 contains a denial-of-service vulnerability in the HTTP/1.1 chunked...","description":"facil.io 0.7.5 through 0.7.6 contains a denial-of-service vulnerability in the HTTP/1.1 chunked transfer encoding parser that allows unauthenticated remote attackers to crash the server by sending a negative chunk size value. Attackers can send a single POST request with a Transfer-Encoding: chunked header containing a leading minus sign in the chunk size field, causing the parser in http1_parser.h to compute a large positive integer from the negated value, corrupting internal state and moving the read pointer into unmapped memory resulting in a fault.","status":"published","published":"2026-07-27T18:31:49Z","modified":"2026-07-31T21:31:51Z","cvss":[{"version":"4.0","score":8.7,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-125"],"updated_at":"2026-11-02T15:10:00.950607Z"}],"nvd":[{"id":"CVE-2026-66731","description":"facil.io 0.7.5 through 0.7.6 contains a denial-of-service vulnerability in the HTTP/1.1 chunked transfer encoding parser that allows unauthenticated remote attackers to crash the server by sending a negative chunk size value. Attackers can send a single POST request with a Transfer-Encoding: chunked header containing a leading minus sign in the chunk size field, causing the parser in http1_parser.h to compute a large positive integer from the negated value, corrupting internal state and moving the read pointer into unmapped memory resulting in a fault.","status":"published","published":"2026-07-27T17:16:42.793Z","modified":"2026-10-24T13:10:00.147Z","cvss":[{"version":"4.0","score":8.7,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-125"],"updated_at":"2026-11-02T14:12:33.249634Z"}],"osv":[{"id":"CVE-2026-66731","title":"facil.io 0.7.5 - 0.7.6 HTTP/1.1 Chunked Transfer Encoding Parser Crash DoS","description":"facil.io 0.7.5 through 0.7.6 contains a denial-of-service vulnerability in the HTTP/1.1 chunked transfer encoding parser that allows unauthenticated remote attackers to crash the server by sending a negative chunk size value. Attackers can send a single POST request with a Transfer-Encoding: chunked header containing a leading minus sign in the chunk size field, causing the parser in http1_parser.h to compute a large positive integer from the negated value, corrupting internal state and moving the read pointer into unmapped memory resulting in a fault.","status":"published","published":"2026-07-27T16:57:01.077Z","modified":"2026-10-28T02:30:33.139594313Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"cwes":["CWE-125"],"updated_at":"2026-11-02T15:45:14.46177Z"}]}}