How to Fix CVE-2026-35538: Webmail (Bundle Sibling)
*By Sai Kiran Pandrala*
Last verified: 2026-05-25
| Severity | CVSS 3.1, Low |
|---|---|
| Actively exploited? | No |
| Affected | Roundcube Webmail (0 < 1.5.14, 1.6.0 < 1.6.14) |
| Fixed in | Same patched build as CVE-2026-35537 |
| Type (CWE) | CWE-88: Improper Neutralization of Argument Delimiters in a Command ('Argument Injection') |
CVE-2026-35538 is a sibling vulnerability in the same Roundcube Webmail advisory bundle as CVE-2026-35537. The same patched build closes every CVE in the bundle, so the remediation procedure for CVE-2026-35538 matches the primary write-up.
What is different about CVE-2026-35538?
An issue was discovered in Roundcube Webmail before 1.5.14 and 1.6.14. Unsanitized IMAP SEARCH command arguments could lead to IMAP injection or CSRF bypass during mail search.
Impact is consistent with the bundle: cross-site request forgery against an authenticated user. The patched build closes every code path in the advisory in one update.
How to fix CVE-2026-35538
Apply the patched build per the primary write-up: How to Fix CVE-2026-35537.
For a quick check, confirm the running version of Webmail:
# Confirm the installed version via your package manager
dpkg -l | grep -i webmail # Debian/Ubuntu
rpm -qa | grep -i webmail # RHEL/CentOS/Rocky
Frequently asked questions
Is CVE-2026-35538 being actively exploited?
Not at the time of writing. It is not listed in CISA's Known Exploited Vulnerabilities catalog. That status can change, so monitor the vendor advisory and the KEV catalog if the system is exposed.
How severe is CVE-2026-35538?
CVSS rates it 3.1 (Low). Use that score to set your patch priority alongside the other items in your queue.
Do I have to take Webmail offline to apply the patch?
It depends on the deployment. High-availability or clustered installs can usually patch one node at a time with no full outage. Standalone installs typically need a short restart. Always follow the vendor's documented upgrade steps.
What if my vulnerability scanner still flags CVE-2026-35538 after I patch?
Re-run the scan after a service restart, then confirm the scanner's plugin set is up to date. Some scanners detect by banner version only and lag the official fix metadata by a release.
References
- Official vendor advisory: https://roundcube.net/news/2026/03/18/security-updates-1.7-rc5-1.6.14-1.5.14
- NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2026-35538
- CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
- Primary write-up: How to Fix CVE-2026-35537
*Written by Sai Kiran Pandrala. Last verified 2026-05-25. Part of the Roundcube Webmail advisory bundle. Full procedure at how-to-fix-cve-2026-35537.*