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Fencer Intel
medium 6.1

CVE-2026-35539 json

Roundcube Webmail: Insufficient HTML attachment sanitization in preview mode

published 7mo ago modified 3mo ago also GHSA-x4q5-8j5g-hpjc , EUVD-2026-18581

cvss
6.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 17%
public exploits
0
none known

Summary

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.

Patch / fix

  • packagist roundcube/roundcubemail 1.7-rc5
  • Roundcube Webmail 1.5.14, 1.6.14
  • roundcube Debian 12 1.6.5+dfsg-1+deb12u8
  • roundcube Debian 13 1.6.15+dfsg-0+deb13u1
  • roundcube Debian 14 1.6.14+dfsg-1

debian advisories DEBIAN-CVE-2026-35539

Is CVE-2026-35539 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-35539 updated cvss 5.4

roundcubemail: Roundcube Webmail: Cross-Site Scripting via HTML attachment preview

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
7mo ago

Exploit prediction

0.26% chance of exploitation in the next 30 days, higher than 17% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
GitHub 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
packagist roundcube/roundcubemail
>=1.7-beta, <1.7-rc5
1.7-rc5

Affected products

  • Roundcube Webmail

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.