CVE-2026-27602 is a high-severity (CVSS 7.2) OS Command Injection vulnerability in modoboa. A fix is available for modoboa — see the affected versions and patch details below.
Modoboa has an OS Command Injection
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-27602.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-27602 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
modoboaReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
exec_cmd() in modoboa/lib/sysutils.py always runs subprocess calls with shell=True. Since domain names flow directly into shell command strings without any sanitization, a Reseller or SuperAdmin can include shell metacharacters in a domain name to run arbitrary OS commands on the server.
Details
The root cause is in modoboa/lib/sysutils.py:31:
kwargs["shell"] = True
process = subprocess.Popen(cmd, **kwargs)
When a create a domain is created with DKIM enabled, the domain name gets embedded into a shell command like this:
exec_cmd(f"openssl genrsa -out {dkim_storage_dir}/{domain.name}.pem {key_size}")
If the domain name contains something like $(id>/tmp/proof).example.com, the shell executes the injected command before running openssl.
The same pattern appears in several other places:
modoboa/admin/jobs.py:38— mailbox rename viamvusingfull_addressmodoboa/amavis/lib.py:202—sa-learnusingdomain.namemodoboa/admin/models/mailbox.py:150—doveadm userusingfull_addressmodoboa/maillog/graphics.py:105–107—rrdtoolusingdomain.namemodoboa/webmail/models.py:54–57—doveadm move/deleteusingaccount.email
PoC
- Deploy modoboa <= 2.7.0
- Log in as a Reseller or SuperAdmin
- Create a new domain named
$(id>/tmp/proof).example.comwith DKIM enabled - SSH into the server and read
/tmp/proof
Something like this will be displayed:
uid=0(root) gid=0(root) groups=0(root)
Confirmed on commit b521bcb4f (latest main at time of discovery).
Impact
An attacker with Reseller-level access (or higher) can execute arbitrary OS commands on the mail server — in a typical Modoboa deployment this means running as root. All six identified sinks are reachable through normal application workflows.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | modoboa | all versions | 2.7.1pip install --upgrade 'modoboa==2.7.1' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for modoboa, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update modoboa to 2.7.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27602 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-27602 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-27602. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-27602 in your dependencies?
O3 Security finds CVE-2026-27602 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.