---
id: "CVE-2026-127121"
page: "https://infrastack.ai/live/CVE-2026-127121"
kind: "vulnerability"
aliases: ["CVE-2026-127121"]
title: "SOGo: forged signed email replaces a contact's S/MIME certificate"
severity: "high"
cvss: 7.1
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["email", "other", "self-hosted", "smime", "sogo"]
not_affected_if: ["no-smime-use"]
published_at: "2026-11-12T16:19:07+00:00"
first_seen_at: "2026-11-12T16:44:02+00:00"
updated_at: "2026-11-12T16:45:41+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-127121", "first_seen_at": "2026-11-12T16:44:02+00:00"}]
exploit_sources: []
---

# SOGo: forged signed email replaces a contact's S/MIME certificate

Link for people: https://infrastack.ai/live/CVE-2026-127121 (this .md is for agents)

SOGo, a groupware server for mail, calendars and contacts, accepts a spoofed signed email and stores the attacker's self-signed certificate on the victim's contact card without checking the signature. Later encrypted mail to that contact can be decrypted with the attacker's private key.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed SOGo version against the fixed version below.

## Fix

- SOGo: `5.12.13` or later (per the vulnerability description: before 5.12.13 is affected)

## Timeline

- 2026-11-12T16:44:02+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-127121

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/sogo-before-s-mime-certificate-spoofing-via-uixmailview
- [fix] Release notes: github.com https://github.com/Alinto/sogo/releases/tag/SOGo-5.12.13

## From the sources

SOGo before 5.12.13 contains an improper cryptographic signature verification vulnerability that allows remote attackers to replace a victim's contact S/MIME certificate by sending a spoofed multipart/signed message with a mismatched signature and an impersonated From address. Attackers can deliver a crafted CMS signedData object containing their own self-signed certificate, which SOGo's UIxMailView stores on the contact card without validating signature authenticity or certificate identity, enabling subsequent encrypted communications to be decrypted with the attacker's private key.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_