CVE-2026-26079Network attack vector

CSS injection via malformed comment parsing

Published Feb 11, 2026 · Updated Feb 11, 2026

CSS injection in Roundcube Webmail before 1.5.13 and 1.6.0 through 1.6.12 allows remote attackers to alter rendered message styles. The rcube_utils::mod_css_styles parser removes comments inconsistently, allowing malformed comment and brace sequences to escape intended CSS scoping and sanitization. A recipient must open the crafted message, after which attacker-controlled CSS can manipulate the displayed webmail interface.

CVSS severity4.7
Medium
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CSS injection in Roundcube Webmail before 1.5.13 and 1.6.0 through 1.6.12 allows remote attackers to alter rendered message styles. The rcube_utils::mod_css_styles parser removes comments inconsistently, allowing malformed comment and brace sequences to escape intended CSS scoping and sanitization. A recipient must open the crafted message, after which attacker-controlled CSS can manipulate the displayed webmail interface.

The record

CVE
CVE-2026-26079
Published
Feb 11, 2026
Updated
Feb 11, 2026
Vendor
Roundcube
Product
Roundcube Webmail
Classifications
CWE-829, T1204
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <1.5.13
  2. Affected versionversion=1.6.0 <1.6.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Roundcube · Roundcube Webmailversion=0 <1.5.13; version=1.6.0 <1.6.13

Published CVSS scores

4.7MITRECVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-829Inclusion of Functionality from Untrusted Control Sphere
T1204User Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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