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Fencer Intel
medium 5.4

CVE-2026-35540 json

Roundcube Webmail: Insufficient CSS sanitization in HTML e-mail messages

published 7mo ago modified 3mo ago also GHSA-vxg2-hhgr-37fx , EUVD-2026-18583

cvss
5.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 34%
public exploits
0
none known

Summary

An issue was discovered in Roundcube Webmail 1.6.0 before 1.6.14. Insufficient Cascading Style Sheets (CSS) sanitization in HTML e-mail messages may lead to SSRF or Information Disclosure, e.g., if stylesheet links point to local network hosts.

Patch / fix

  • packagist roundcube/roundcubemail 1.7-rc5
  • Roundcube Webmail 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-2026-35540

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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-2026-35540 updated cvss 6.1

roundcubemail: Roundcube Webmail: SSRF via insufficient CSS sanitization

  • 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

0.40% chance of exploitation in the next 30 days, higher than 34% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 5.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
GitHub 3.1 5.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/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-669 Incorrect Resource Transfer Between Spheres
  • CWE-918 Server-Side Request Forgery

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.