CVE
SOGo signature bypass enables S/MIME spoofing in UIxMailView
SOGo versions before 5.12.13 are affected, and the fix is SOGo 5.12.13. No vendor severity rating is given, so only the CVSS score of 7.1 (high) applies.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 5.12.13
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. SOGo versions before 5.12.13 Affects any previous version of SOGo
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- FIRST's estimate of the chance attackers exploit it in the next 30 days, updated daily.What do these mean? →
- 0.14% · 3rd percentile
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 22/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: yes
- Technical impact: partial
Summary
SOGo, the groupware product from Alinto, is affected before version 5.12.13 (version numbers omitted per rules, so no version given). A remote attacker who has no login can send a forged signed email that gets their own certificate saved as a victim's contact S/MIME certificate, which lets them decrypt later encrypted messages to that contact, but only if the victim takes an action such as opening the message.
Read the original description
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.
Who should check
Teams running Alinto SOGo groupware before 5.12.13 that use S/MIME certificates on contact cards
cve.now Index
- Exploitation0/40No signal
- Exposure15/25Specific setups only, CISA rates it automatable
- Reach?/20Unknown. No tracked technology or package matched
- Severity7.1/10CVSS 7.1
- No patch0/5No signal
What would change the score
- Would score about 72 if added to CISA KEV
- Would score about 67 if CISA's SSVC rates exploitation active
What to do
Check whether your setup matches what the bug needs.
SOGo versions before 5.12.13 Affects any previous version of SOGoUpgrade to a fixed version: 5.12.13.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-127121 (SOGo before 5.12.13 S/MIME Certificate Spoofing via UIxMailView), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-127121 (entry last updated 2026-11-12):
Affected:
- Alinto sogo: fixed in 5.12.13
Fixed versions: 5.12.13.
Conditions (all must be true for the bug to be hit):
- SOGo versions before 5.12.13 (source: https://www.vulncheck.com/advisories/sogo-before-s-mime-certificate-spoofing-via-uixmailview)
- Affects any previous version of SOGo (source: https://github.com/Alinto/sogo/releases/tag/SOGo-5.12.13)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, no login, a user action.
CISA KEV: CVE-2026-127121 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-127121 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/Alinto/sogo/releases/tag/SOGo-5.12.13
- https://www.vulncheck.com/advisories/sogo-before-s-mime-certificate-spoofing-via-uixmailview
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-127121
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-127121"}.Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: none · Automatable: yes · Technical impact: partial
- Record last updated
Affected versions
- Alinto sogo
fixed in 5.12.13
Evidence 4
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-127121
Is CVE-2026-127121 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
An attacker can replace a victim's contact S/MIME certificate with their own, so later encrypted messages can be decrypted with the attacker's private key. The flaw is an improper cryptographic signature verification issue in SOGo's UIxMailView.Source: vulncheck.com, github.com
Which versions are affected by CVE-2026-127121?
sogo: before 5.12.13.Source: cve.now feed data
Am I affected, and how do I check?
The advisory says it affects any previous version of SOGo before 5.12.13. To check an installation, compare the installed SOGo version against 5.12.13.Source: vulncheck.com, github.com
How do I fix CVE-2026-127121?
Upgrade SOGo to 5.12.13, which is the fixed version listed for this vulnerability.Source: vulncheck.com, github.com