# CVE-2026-127121: SOGo improper cryptographic signature verification in S/MIME

Source: https://junglewise.ai/threats/cve-2026-127121-sogo-before-5-12-13-contains-an-improper-cryptographic-signature  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-12. Updated: 2026-11-12  
License: CC BY 4.0 with a link back

CVE-2026-127121 · Severity: medium · CVSS 6.5 · Published 2026-11-12

SOGo is a groupware suite that manages email, calendars, and contacts. An attacker can send a spoofed email that tricks SOGo into storing the attacker's certificate as a contact's trusted encryption key, allowing the attacker to decrypt future encrypted messages intended for that contact. This enables man-in-the-middle attacks on encrypted communications.

Technologies: [Alinto Sogo](https://junglewise.ai/threats/technologies/sogo). Vendors: [Alinto](https://junglewise.ai/threats/vendors/alinto).

## Quick answers

**Is CVE-2026-127121 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-127121 being exploited in the wild.

**How severe is CVE-2026-127121?** Medium severity, with a CVSS score of 6.5, published 12 November 2026.

**Which products and versions are affected?** Alinto Sogo before 5.12.13.

**Is there a fix for CVE-2026-127121?** Yes: fixed in SOGo 5.12.13. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-127121 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-127121?** Check whether you run Alinto Sogo at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in SOGo 5.12.13

## Technical details

SOGo's UIxMailView component fails to validate S/MIME signature authenticity when processing multipart/signed messages, accepting a crafted CMS signedData object with a mismatched signature and storing the attacker's self-signed certificate on the contact card without identity verification. The vulnerability requires network access and user interaction (viewing a crafted email), and allows an attacker to intercept and decrypt subsequent encrypted communications between the victim and the impersonated contact.

## Affected products

- Alinto SOGo before 5.12.13

## Timeline

- 2026-11-12: disclosed
- 2026-11-04: patched

## References

- [https://github.com/Alinto/sogo/releases/tag/SOGo-5.12.13](https://github.com/Alinto/sogo/releases/tag/SOGo-5.12.13)
- [https://www.vulncheck.com/advisories/sogo-before-s-mime-certificate-spoofing-via-uixmailview](https://www.vulncheck.com/advisories/sogo-before-s-mime-certificate-spoofing-via-uixmailview)

## Related threats

- [SOGo server-side request forgery in Calendar web subscription](https://junglewise.ai/threats/cve-2026-127145-sogo-before-5-12-13-contains-a-server-side-request-forgery)
- [SOGo denial of service via IMAP greeting timeout](https://junglewise.ai/threats/cve-2026-127141-sogo-before-5-12-13-contains-a-denial-of-service-vulnerability)
- [SOGo Sieve script injection in notification address](https://junglewise.ai/threats/cve-2026-127135-sogo-before-5-12-13-contains-a-sieve-script-injection)
- [SOGo missing rate limiting in TOTP verification](https://junglewise.ai/threats/cve-2026-127131-sogo-before-5-12-13-contains-a-missing-rate-limiting)
- [SOGo improper restriction of excessive authentication attempts](https://junglewise.ai/threats/cve-2026-127111-sogo-before-5-12-13-contains-an-improper-restriction-of)