CriticalCVE-2024-37383

    RoundCube Webmail Cross-Site Scripting (XSS) Vulnerability (CVE-2024-37383)

    Published In CISA KEV since Sources: Debian, pwn.watch, CVE.org

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    What is affected, what to do

    Roundcube Webmail before 1.5.7 and 1.6.x before 1.6.7 allows XSS via SVG animate attributes.

    The vulnerability is being actively exploited; treat it as a priority. Update Roundcube Webmail to version 1.5.7, Roundcube Webmail to version 1.6.7. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Roundcube Webmail lt *..1.5.7
    • Roundcube Webmail lt 1.6.0..1.6.7
    • Debian Linux eq 10.0..10.0
    Fixed in
    • Roundcube Webmail 1.5.7
    • Roundcube Webmail 1.6.7

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    6.1

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    6.1

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: Debian, pwn.watch, CVE.org

    74.0 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.48

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    214.98 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

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    actively exploited
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    6.1 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    6.1
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

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    74.0 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    99.48
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · not automatable · Technical impact: partial
    Source: CISA Vulnrichment, as of 25 October 2024
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-79

    Response and mitigation

    Why act now?

    Prioritisation rationale

    Exploitation is triggered by a crafted email: the victim only has to open the message in Roundcube, with no further interaction needed. The attacker needs no authentication and gains JavaScript execution in the webmail session context, which is typically used to overlay fake login prompts, harvest credentials and exfiltrate mail and contacts. Roundcube is widely deployed across government, universities, hosters and mid-market firms, and it is a recurring target of espionage campaigns against public-sector bodies. The moderate base score is misleading: exploitation likelihood is among the very highest observed. Treat this CVE as high to critical for KRITIS operators and public institutions with internet-facing webmail. CISA does not flag known ransomware use.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Patch: Upgrade every Roundcube instance to 1.5.7 (1.5 LTS branch) or 1.6.7 (1.6 branch) or later. Check the running version with grep RCMAIL_VERSION program/include/iniset.php in the install directory.
      • Distro packages: On Debian 10 (buster), update the roundcube package from Debian LTS. A patch is available from the vendor — look up the fixed package version in the Debian LTS advisory (DLA). Do the same for hosting panels that bundle Roundcube (cPanel, Plesk, ISPConfig).
      • Inventory: Enumerate all webmail endpoints, including forgotten test and legacy instances and those run by hosting providers. Unpatched internet-facing instances come first; if needed, temporarily put them behind a VPN or a pre-authenticating reverse proxy.
      • Compromise sweep: Use the mail gateway or IMAP search to find HTML messages containing inline <svg> with <animate elements. For any affected accounts, reset passwords, kill active sessions (purge the Roundcube session table) and review forwarding and filter rules.
      • User advisory: Send a short warning that an unexpected re-login prompt appearing after opening a message in Roundcube must not be filled in and should be reported to the SOC.

    2. Runbook step 2

      Mitigation layers

      • Mail gateway (content filtering): Quarantine inbound HTML mail with inline SVG that contains <animate or <set combined with attributeName (including whitespace or case variants such as "href ") and javascript:. Alternatively, strip inline SVG and SVG attachments entirely.
      • Application config: Until patched, set $config['prefer_html'] = false; in config/config.inc.php so mail renders as plain text by default. Also set $config['show_images'] = 0; to stop external resources loading automatically.
      • HTTP hardening (reverse proxy/WAF): Enforce a strict Content-Security-Policy without unsafe-inline for scripts where your Roundcube build tolerates it (test first). Restrict connect-src and form-action to your own origin to hinder exfiltration and fake login forms. Serve session cookies with HttpOnly, Secure and SameSite=Strict.
      • Network segmentation: Restrict internet access to webmail via VPN or a zero-trust proxy. Limit the Roundcube server's egress to its IMAP and SMTP backends.
      • IAM: Enable MFA for webmail (e.g. the twofactor_gauthenticator plugin or upstream SSO) so that harvested credentials are of much less use to an attacker.

    3. Runbook step 3

      Detection rules

      • Mail gateway/MTA logs: Look for messages whose body contains <animate together with attributeName and javascript: or base64. Sigma shape: selection: body|contains|all: ['<svg', '<animate', 'attributeName'].
      • Proxy/firewall telemetry (Zeek/Suricata): Browser requests to unfamiliar external domains within seconds of a Roundcube ?_task=mail&_action=show or _action=preview request. POSTs carrying _user/_pass fields to foreign domains are a strong signal. SPL: index=proxy http_method=POST form_data="*_pass*" NOT dest_domain="webmail.example.com".
      • Roundcube logs (logs/userlogins.log, web server access log): The same account logging in from a new country or ASN shortly after opening a suspicious message, and spikes in _action=plugin.managesieve-save (new Sieve forwarding rules).
      • IMAP/mail server logs (Dovecot): Bulk FETCH or export activity from the Roundcube session IP, new forwards to external addresses and address-book changes.
      • Endpoint/EDR: Browser processes saving files (e.g. .eml, .zip) from blob or data URLs after visiting the webmail domain, which points to client-side exfiltration.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Roundcube Webmail before 1.5.7 and 1.6.x before 1.6.7 allows XSS via SVG animate attributes.

    Source: Debian Security Advisories, pwn.watch, NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    roundcubewebmail
    • 1.6.0 – < 1.6.7
    • < 1.5.7
    • 1.6.7
    • 1.5.7

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebiandebian_linux10.0
    Linuxdebianroundcubebookworm
    Linuxdebianroundcubebullseye

    Weakness classes (CWE)

    • CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

      Base

      The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

      Entry at MITRE CWE-79

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited

    References & sources

    • github.comroundcube/roundcubemail/commit/43aaaa528646877789ec028d87924ba1…Patch
    • github.comRoundcube advisory: CVE-2024-37383Release notes, pwn-watch
    • github.comroundcube/roundcubemail/releases/tag/1.5.7Release notes
    • lists.debian.org[debian-lts-announce] 20240617 [SECURITY] [DLA 3835-1] roundcube security updateMailing list, Mailing list, Third-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2024-37383government-resource, US government resource
    • pwn.watchpwn.watch: RoundCube Webmail Cross-Site Scripting (XSS)pwn-watch
    • github.comRoundcube advisory: CVE-2024-37383pwn-watch
    • NVD (NIST)NVD: CVE-2024-37383pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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