{"cve":"CVE-2023-51766","nvd":{"published":"2023-12-24T06:15:07.673","modified":"2026-06-17T06:41:37.057","status":"Modified","description":"Exim before 4.97.1 allows SMTP smuggling in certain PIPELINING/CHUNKING configurations. Remote attackers can use a published exploitation technique to inject e-mail messages with a spoofed MAIL FROM address, allowing bypass of an SPF protection mechanism. This occurs because Exim supports <LF>.<CR><LF> but some other popular e-mail servers do not.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","score":5.3},"cwes":["CWE-345"],"references":["http://www.openwall.com/lists/oss-security/2023/12/24/1","http://www.openwall.com/lists/oss-security/2023/12/25/1","http://www.openwall.com/lists/oss-security/2023/12/29/2","http://www.openwall.com/lists/oss-security/2024/01/01/1","http://www.openwall.com/lists/oss-security/2024/01/01/2"],"products":["debian:debian_linux","exim:exim","fedoraproject:extra_packages_for_enterprise_linux","fedoraproject:fedora"],"source":"nvd","synced_at":"2026-10-19T21:43:38.875533635+00:00"},"epss":{"cve":"CVE-2023-51766","score":0.01102,"percentile":0.65717,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}