Cyber Resilience

CVE-2023-5631

XSS in Roundcube Webmail ≤ 1.4.15

CISA KEVActive ExploitationEUVD ExploitedPublic PoCXSS
Published
18 October 2023
Modified
30 October 2025
KEV Added
26 October 2023
Patch / advisory
View advisory
CVSS Score v3.1 6.1
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS Score 0.76 99.5th percentile
Risk Priority 75 floored blend · peak EPSS

Summary

CVE-2023-5631 is a medium-severity Cross-site Scripting (CWE-79) vulnerability in Roundcube Webmail. Its CVSS base score is 6.1 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Browser Session Hijacking (T1185); ranked in the top 0.5% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

Roundcube webmail before version 1.4.15, 1.5.x before 1.5.5, and 1.6.x before 1.6.4 is affected by a stored cross-site scripting flaw tracked as CVE-2023-5631. The issue resides in the HTML sanitization logic of program/lib/Roundcube/rcube_washtml.php, which fails to properly neutralize a crafted SVG document embedded in an HTML email message and thereby permits arbitrary JavaScript execution.

A remote attacker can exploit the vulnerability by sending a victim a malicious HTML email containing the crafted SVG. When the recipient views the message through the Roundcube interface, the injected script runs in the application context with the victim’s privileges, enabling actions such as cookie theft or mailbox manipulation under the CVSS vector AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

Public advisories and the referenced Roundcube commit direct administrators to upgrade to the fixed releases 1.4.15, 1.5.5, or 1.6.4; distribution trackers such as the Debian bug report and oss-security postings likewise emphasize applying these updates as the primary mitigation.

The associated EPSS score has reached a peak of 0.8520 with a current value of 0.8324, indicating sustained exploitation interest after disclosure.

OWASP Top 10 for Web (2025)

A05:2025 Injection

EU & UK References

Vulnerability Data

Roundcube before 1.4.15, 1.5.x before 1.5.5, and 1.6.x before 1.6.4 allows stored XSS via an HTML e-mail message with a crafted SVG document because of program/lib/Roundcube/rcube_washtml.php behavior. This could allow a remote attacker to load arbitrary JavaScript code.

CWE(s)
CWE-79
KEV Date Added
26 October 2023

Related Threats

MITRE ATT&CK Enterprise Techniques

T1185 Browser Session Hijacking Collection
Adversaries may take advantage of security vulnerabilities and inherent functionality in browser software to change content, modify user-behaviors, and intercept information as part of various browser session hijacking techniques.
attack.mitre.org →
T1539 Steal Web Session Cookie Credential Access
An adversary may steal web application or service session cookies and use them to gain access to web applications or Internet services as an authenticated user without needing credentials.
attack.mitre.org →
T1659 Content Injection Initial Access
Adversaries may gain access and continuously communicate with victims by injecting malicious content into systems through online network traffic.
attack.mitre.org →
T1189 Drive-by Compromise Initial Access
Adversaries may gain access to a system through a user visiting a website over the normal course of browsing.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2020-35730Same product: Debian Debian Linuxboth on KEV
CVE-2020-13965Same product: Debian Debian Linuxboth on KEV
CVE-2023-47272Same product: Debian Debian Linux
CVE-2023-43770Same product: Debian Debian Linuxboth on KEV
CVE-2018-6882Same product class: email / collaborationboth on KEV
CVE-2022-27926Same product class: email / collaborationboth on KEV
CVE-2023-34192Same product class: email / collaborationboth on KEV
CVE-2023-37580Same product class: email / collaborationboth on KEV
CVE-2023-5480Same product: Debian Debian Linux
CVE-2023-43102Same product class: email / collaboration

Affected Assets

roundcube
webmail
≤ 1.4.15 · 1.5.0 — 1.5.5 · 1.6.0 — 1.6.4
debian
debian linux
10.0, 11.0, 12.0
fedoraproject
fedora
39

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V1.1.2
  • V1.3.2

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

CA-8 Penetration Testing
addresses: CWE-79

Penetration testing submits XSS payloads to web applications, detecting cross-site scripting flaws for subsequent remediation.

SI-10 Information Input Validation
addresses: CWE-79

Validates web inputs to reject script-related content that could produce XSS.

SI-15 Information Output Filtering
addresses: CWE-79

Output validation against expected content can reject or sanitize script content in generated web pages, reducing XSS exploitability.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly target introduction of XSS via coding standards/testing (mostly), yet the single broad outcome leaves many specific neutralization vectors unaddressed (partial).

PR.PS-02 partial match
prevents

Patching and EOL replacement can remediate known XSS instances in libraries or frameworks (partial) but do nothing to enforce input neutralization in application code (none).

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Secure-coding testing and automated code-analysis tools are applied to detect improper neutralization of script-related content during web-page generation.

A.5.6 Contact with special interest groups partial match
prevents

Knowledge exchange on emerging attack techniques and patches reduces the likelihood that cross-site scripting flaws remain unaddressed in deployed applications.

A.5.7 Threat intelligence partial match
prevents

Operational indicators of compromise for web-application attacks can be incorporated into WAF or input-filtering rules, lowering the likelihood that unsanitized data reaches the browser.

A.8.25 Secure development life cycle partial match
prevents

Requiring language-specific secure-coding standards and automated scanning during the SDLC catches missing output encoding or improper neutralization of untrusted data before the software reaches production.

A.8.28 Secure coding partial match
prevents

Secure-coding standards, SAST scans and removal of insecure code samples together eliminate the failure to neutralize script content that produces cross-site scripting flaws.

A.8.7 Protection against malware none match
none

Webpage malware scanning and block-listing of known malicious sites reduce the likelihood that reflected or stored script payloads reach a user’s browser.

References