How severe is CVE-2026-35539?

CVE-2026-35539 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-35539 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-35539?

CVE-2026-35539 affects Roundcube Webmail. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-35539?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-35539 have an EU (EUVD) identifier?

Yes. CVE-2026-35539 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18581.

When was CVE-2026-35539 published?

CVE-2026-35539 was published on 2026-04-03 and last updated on 2026-06-17.

CVE-2026-35539

CVE-2026-35539 is a medium-severity vulnerability in Roundcube Webmail with a CVSS 3.x base score of 6.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
EPSS exploit prediction: 0% (16th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-18581
Weakness: CWE-79
Affected product: Roundcube Webmail
Published: 2026-04-03
Last modified: 2026-06-17

Description

An issue was discovered in Roundcube Webmail before 1.5.14 and 1.6.14. XSS exists because of insufficient HTML attachment sanitization in preview mode. A victim must preview a text/html attachment.

Frequently asked questions

What is CVE-2026-35539?: An issue was discovered in Roundcube Webmail before 1.5.14 and 1.6.14. XSS exists because of insufficient HTML attachment sanitization in preview mode. A victim must preview a text/html attachment.
How severe is CVE-2026-35539?: CVE-2026-35539 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-35539 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-35539?: CVE-2026-35539 affects Roundcube Webmail. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-35539?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-35539 have an EU (EUVD) identifier?: Yes. CVE-2026-35539 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18581.
When was CVE-2026-35539 published?: CVE-2026-35539 was published on 2026-04-03 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:roundcube:webmail:*:*:*:*:*:*:*:*

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