{"id":"CVE-2026-84465","aliases":["EUVD-2026-87265","GHSA-m9ff-hjr3-93h4"],"status":"published","title":"Zammad: S/MIME signature verification allows forged sender impersonation","description":"Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, when Zammad checks the digital signature on an incoming S/MIME-signed email, it does not verify that the signing certificate is genuinely trusted, it only checks whether a certificate with a matching name is already stored in the system. An attacker can create their own certificate using the name of a real, previously trusted sender and use it to send a forged email. Zammad will display that email with the same \"validly signed\" indicator as a genuine message from the real sender, even though the attacker never had access to that sender's actual certificate or private key. This issue is fixed in version 7.1.2.","severity":{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00124,"percentile":0.0212,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-290","CWE-295","CWE-347"],"published":"2026-09-25T18:19:58Z","modified":"2026-10-28T02:30:30Z","products":[{"vendor":"zammad","product":"zammad"}],"references":[{"url":"https://github.com/zammad/zammad/security/advisories/GHSA-m9ff-hjr3-93h4","tags":["x_refsource_CONFIRM","advisory"]},{"url":"https://github.com/zammad/zammad/commit/9a07d0b8214ac4e8e10c23fce71d613bd0625524","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84465.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-84465","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-84465","title":"Zammad: S/MIME signature verification allows forged sender impersonation","description":"Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, when Zammad checks the digital signature on an incoming S/MIME-signed email, it does not verify that the signing certificate is genuinely trusted, it only checks whether a certificate with a matching name is already stored in the system. An attacker can create their own certificate using the name of a real, previously trusted sender and use it to send a forged email. Zammad will display that email with the same \"validly signed\" indicator as a genuine message from the real sender, even though the attacker never had access to that sender's actual certificate or private key. This issue is fixed in version 7.1.2.","status":"published","published":"2026-09-25T18:19:58.735Z","modified":"2026-09-29T18:08:05.375Z","cvss":[{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high","assessor":"cna"}],"cwes":["CWE-290","CWE-295","CWE-347"],"updated_at":"2026-11-02T14:20:08.009733Z"}],"euvd":[{"id":"EUVD-2026-87265","description":"Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, when Zammad checks the digital signature on an incoming S/MIME-signed email, it does not verify that the signing certificate is genuinely trusted, it only checks whether a certificate with a matching name is already stored in the system. An attacker can create their own certificate using the name of a real, previously trusted sender and use it to send a forged email. Zammad will display that email with the same \"validly signed\" indicator as a genuine message from the real sender, even though the attacker never had access to that sender's actual certificate or private key. This issue is fixed in version 7.1.2.","status":"published","published":"2026-09-25T18:19:58Z","modified":"2026-09-29T18:08:05Z","cvss":[{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"updated_at":"2026-11-02T17:27:51.524944Z"}],"nvd":[{"id":"CVE-2026-84465","description":"Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, when Zammad checks the digital signature on an incoming S/MIME-signed email, it does not verify that the signing certificate is genuinely trusted, it only checks whether a certificate with a matching name is already stored in the system. An attacker can create their own certificate using the name of a real, previously trusted sender and use it to send a forged email. Zammad will display that email with the same \"validly signed\" indicator as a genuine message from the real sender, even though the attacker never had access to that sender's actual certificate or private key. This issue is fixed in version 7.1.2.","status":"published","published":"2026-09-25T19:17:58.123Z","modified":"2026-09-29T19:17:27.05Z","cvss":[{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/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"}],"cwes":["CWE-290","CWE-295","CWE-347"],"updated_at":"2026-11-02T14:12:51.721923Z"}],"osv":[{"id":"CVE-2026-84465","title":"Zammad: S/MIME signature verification allows forged sender impersonation","description":"Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, when Zammad checks the digital signature on an incoming S/MIME-signed email, it does not verify that the signing certificate is genuinely trusted, it only checks whether a certificate with a matching name is already stored in the system. An attacker can create their own certificate using the name of a real, previously trusted sender and use it to send a forged email. Zammad will display that email with the same \"validly signed\" indicator as a genuine message from the real sender, even though the attacker never had access to that sender's actual certificate or private key. This issue is fixed in version 7.1.2.","status":"published","published":"2026-09-25T18:19:58.735Z","modified":"2026-10-28T02:30:30.81335653Z","cvss":[{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-290","CWE-295","CWE-347"],"updated_at":"2026-11-02T15:45:18.482949Z"}]}}