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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 13 Jul 2023.
FedoraOperating system · Fedoraproject

CVE-2020-35730

MEDIUM · 6.1 CVSS v3.1 Published 2020-12-28
Fix available
A fix is available. Upgrade to 1.2.13 / 1.3.16 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild Remotely reachable No privileges Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An XSS issue was discovered in Roundcube Webmail before 1.2.13, 1.3.x before 1.3.16, and 1.4.x before 1.4.10. The attacker can send a plain text e-mail message, with JavaScript in a link reference element that is mishandled by linkref_addindex in rcube_string_replacer.php.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A stored XSS vulnerability in Roundcube Webmail allows attackers to inject malicious JavaScript via specially crafted plain text emails. The vulnerability exists in the linkref_addindex function within rcube_string_replacer.php, which improperly handles link reference elements in plain text email messages. When recipients view these emails, the injected script executes in their browser context.

MitigationUpgrade Roundcube Webmail to version 1.2.13, 1.3.16, or 1.4.10 or later to obtain the patched version of rcube_string_replacer.php that properly sanitizes link references in plain text emails.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FedoraOperating system
Affected:= 32= 33
Debian LinuxOperating system
Affected:= 9.0
WebmailApplication
Affected:< 1.2.13>= 1.3.0, < 1.3.16>= 1.4, < 1.4.10

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Locate Roundcube installation directory
    Search for the file rcube_string_replacer.php which contains the vulnerable linkref_addindex function, typically found within the Roundcube program or include directory.
    Affected if The file exists in your environment, indicating Roundcube is installed.
  2. Identify installed Roundcube version
    Open the Roundcube version file (commonly version.php in the root directory or program/include/includes.php) and note the version number.
    Affected if Version cannot be determined or falls within < 1.2.13, >= 1.3.0 but < 1.3.16, or >= 1.4 but < 1.4.10.
  3. Confirm plain text email viewing is enabled
    Check Roundcube user preferences or system settings for the default邮件视图选项. The vulnerability affects plain text email rendering specifically.
    Affected if Users can view emails as plain text or plain text is the default view mode.
  4. Verify vulnerable function exists
    Locate rcube_string_replacer.php and search for the linkref_addindex function definition. Inspect how it handles link reference elements.
    Affected if The function processes link references without proper sanitization, allowing script injection.

You are affected if Roundcube Webmail is installed with a version less than 1.2.13, between 1.3.0 and 1.3.15 inclusive, or between 1.4.0 and 1.4.9 inclusive, and plain text email viewing is available.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.2.13 / 1.3.16 / 1.4.10 or later
Fixed in 1.2.131.3.161.4.10
Vendor patch github.com →
Interim mitigation

Upgrade Roundcube Webmail to version 1.2.13, 1.3.16, or 1.4.10 or later to obtain the patched version of rcube_string_replacer.php that properly sanitizes link references in plain text emails.

Recommended fix High confidence

Roundcube Webmail 1.2.13, 1.3.16, or 1.4.10 (depending on your current branch; preferably latest 1.4.x)

  1. 1. Identify the current Roundcube Webmail version by checking the version file or admin interface
  2. 2. Determine which release branch is currently installed (1.2.x, 1.3.x, or 1.4.x)
  3. 3. For Fedora 32/33 or Debian 9.0 systems, update the system package manager (dnf or apt) to fetch the latest security patches
  4. 4. If using the 1.2.x branch, upgrade to version 1.2.13 or later
  5. 5. If using the 1.3.x branch, upgrade to version 1.3.16 or later
  6. 6. If using the 1.4.x branch, upgrade to version 1.4.10 or later (preferably the latest stable 1.4.x release)
  7. 7. Verify the installed version matches the expected fixed version using the admin interface or command line
  8. 8. Test email functionality, particularly plain text email rendering with links
Caveat Minor version upgrades typically have low risk, but review the changelog for any changes to PHP requirements or plugin compatibility before upgrading in production environments

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Fedora Exploited in the wild — priority engagement
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-35730 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data