CVE-2023-5631Known exploitationPublic exploitNetwork attack vector

Stored XSS via whitespace-obfuscated SVG media type

Published Oct 18, 2023 · Updated Oct 21, 2025

Stored XSS in Roundcube Webmail before 1.4.15, 1.5.0 through 1.5.4, and 1.6.0 through 1.6.3 lets remote attackers run JavaScript. The wash_uri path in program/lib/Roundcube/rcube_washtml.php checks the SVG media type before removing whitespace, so a crafted data:image/s vg+xml URI bypasses SVG sanitization. Execution occurs when a user views the attacker's HTML email, and the script runs in the victim's Roundcube browser context.

CVSS severity6.1
Medium
EPSS probability75.87%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Roundcube Webmail before 1.4.15, 1.5.0 through 1.5.4, and 1.6.0 through 1.6.3 lets remote attackers run JavaScript. The wash_uri path in program/lib/Roundcube/rcube_washtml.php checks the SVG media type before removing whitespace, so a crafted data:image/s vg+xml URI bypasses SVG sanitization. Execution occurs when a user views the attacker's HTML email, and the script runs in the victim's Roundcube browser context.

The record

CVE
CVE-2023-5631
Published
Oct 18, 2023
Updated
Oct 21, 2025
Vendor
Roundcube
Product
Roundcube Webmail
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 18, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 21, 2025Record 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=1.4.0 <1.5.14
  2. Affected versionversion=1.5.0 <1.5.4
  3. Affected versionversion=1.6.0 <1.6.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Roundcube · Roundcube Webmailversion=1.4.0 <1.5.14; version=1.5.0 <1.5.4; version=1.6.0 <1.6.3

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
6.1ESETCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

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

Reported exploitation

Technologies

Your stack

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Your stack

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