CVE-2026-30878 — basercms
MEDIUMCVE-2026-30878 is a medium-severity (CVSS 5.3) CWE-285 vulnerability in baserproject/basercms. A fix is available for baserproject/basercms — see the affected versions and patch details below.
baserCMS: Mail Form Acceptance Bypass via Public API
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.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-30878.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
baserproject/basercmsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Summary
A public mail submission API allows unauthenticated users to submit mail form entries even when the corresponding form is not accepting submissions. This bypasses administrative controls intended to stop form intake and enables spam or abuse via the API.
Details
In baserCMS, mail form submissions through the front-end UI are guarded by acceptance checks implemented in MailFrontService::isAccepting(), which ensures that the mail form is currently accepting submissions (e.g. within its configured publish/acceptance window).
These checks are enforced in the UI flow handled by MailController::index() and MailController::confirm()
(e.g. plugins/bc-mail/src/Controller/MailController.php).
However, the public API endpoint:
plugins/bc-mail/src/Controller/Api/MailMessagesController.php::add()
does not invoke MailFrontService::isAccepting() and does not verify whether the mail form is currently accepting submissions. As a result, the API accepts submissions regardless of the form’s acceptance state.
The endpoint does not require authentication. A valid CSRF cookie and token pair is sufficient to create a mail message. This allows submissions even when administrators intentionally disable or close the mail form via the admin UI.
PoC
- In the admin UI, configure a mail form so that it is not accepting submissions (e.g. outside its acceptance period or explicitly closed).
- Obtain a CSRF cookie by accessing the site root:
curl -sS -D - -o - -c /tmp/basercms_cookies.txt 'http://localhost/'
- Extract the CSRF token from the
csrfTokencookie and submit a POST request to the public API endpoint:
curl -sS -D - -o - -X POST 'http://localhost/baser/api/bc-mail/mail_messages/add/1.json'
-H 'Content-Type: application/x-www-form-urlencoded'
-H 'Referer: http://localhost/'
-H 'X-CSRF-Token: <csrf-token-from-cookie>'
-b /tmp/basercms_cookies.txt
--data-urlencode 'name_1=Test'
--data-urlencode 'name_2=User'
--data-urlencode '[email protected]'
--data-urlencode '[email protected]'
--data-urlencode 'category[]=資料請求'
--data-urlencode 'root=検索エンジン'
--data-urlencode 'message=API bypass test'
- The server responds with
200 OKand creates a mail message, even though the form is configured to reject submissions.
Impact
This is an access control / business logic bypass vulnerability.
Administrators rely on the mail form acceptance settings to temporarily or permanently stop form intake (e.g. during maintenance, incidents, or spam attacks). This vulnerability allows attackers to bypass those controls via the public API, enabling unauthorized mail submissions, spam, and operational disruption.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | baserproject/basercms | all versions | 5.2.3composer require baserproject/basercms:^5.2.3 |
Affected Products
basercmsbasercmsDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for baserproject/basercms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update baserproject/basercms to 5.2.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-30878 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2026-30878 in your dependencies?
Find it across Packagist, including transitive dependencies.