CVE-2025-59031: Dovecot FTS Script Info Disclosure Flaw

CVE-2025-59031 Overview

CVE-2025-59031 is an Information Disclosure vulnerability affecting Dovecot's attachment-to-text conversion script. The script unsafely handles zip-style attachments, specifically OOXML documents (such as .docx, .xlsx, and .pptx files). An attacker can craft malicious OOXML documents that cause unintended files on the system to be indexed, with that content subsequently appearing in Full-Text Search (FTS) indexes. This could expose sensitive system files or configuration data to unauthorized users through search results.

Critical Impact

Attackers can leverage specially crafted OOXML documents to force indexing of arbitrary system files, potentially exposing sensitive information through FTS search results.

Affected Products

• Dovecot mail server with the provided attachment-to-text conversion script enabled
• Systems using the default Dovecot FTS indexing with the vulnerable script
• Deployments not using alternative solutions like FTS Tika

Discovery Timeline

• 2026-03-27 - CVE CVE-2025-59031 published to NVD
• 2026-03-30 - Last updated in NVD database

Technical Details for CVE-2025-59031

Vulnerability Analysis

This vulnerability stems from improper handling of zip-style attachments within Dovecot's provided attachment-to-text conversion script. OOXML documents (Office Open XML format) are essentially ZIP archives containing XML files and other resources. When the conversion script processes these attachments for full-text search indexing, it fails to properly validate and sanitize file paths within the archive structure.

The unsafe handling allows an attacker to craft OOXML documents with specially constructed internal references or paths that, when processed by the script, cause the indexer to read and index files outside the intended attachment content. This indexed content then becomes searchable through the FTS system, effectively leaking sensitive system file contents to users who can perform searches.

The vulnerability requires low privileges (an authenticated user who can send or store emails with attachments) and can be exploited remotely over the network without user interaction.

Root Cause

The root cause is classified as CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor). The attachment conversion script lacks proper validation of file paths and references within zip-style archives, allowing path traversal or file reference manipulation within crafted OOXML documents. This design flaw enables the script to access and process files outside the legitimate attachment content boundary.

Attack Vector

The attack requires an authenticated user to submit a specially crafted OOXML document (such as a malicious .docx or .xlsx file) as an email attachment. When Dovecot's FTS system processes this attachment using the vulnerable script, the malicious references within the OOXML structure cause unintended system files to be read and indexed. The attacker (or any user with search access) can then query the FTS indexes to retrieve the leaked content.

The attack can be executed remotely over the network, requires low complexity, and needs only low-privilege authentication. The impact is limited to confidentiality with no direct integrity or availability impact.

Detection Methods for CVE-2025-59031

Indicators of Compromise

• Unusual OOXML attachments with abnormal internal structure or excessive file references
• FTS indexes containing content that appears to originate from system configuration files or other non-email sources
• Email attachments with OOXML files containing path traversal sequences or suspicious symbolic references
• Search queries returning unexpected system file content in FTS results

Detection Strategies

• Monitor the attachment conversion script execution for file access patterns outside expected directories
• Implement file access auditing on sensitive system files to detect unexpected reads during email indexing
• Review FTS index content periodically for anomalous entries that don't correspond to legitimate email content
• Deploy intrusion detection rules to identify OOXML documents with malformed or suspicious internal structures

Monitoring Recommendations

• Enable verbose logging for the Dovecot FTS indexing process to track file access patterns
• Configure file integrity monitoring on sensitive system directories to alert on unexpected reads
• Monitor email attachment processing for unusually large or complex OOXML documents
• Set up alerts for FTS index updates that include content matching sensitive file patterns

How to Mitigate CVE-2025-59031

Immediate Actions Required

• Disable the vulnerable Dovecot-provided attachment-to-text conversion script immediately
• Migrate to alternative FTS solutions such as FTS Tika for attachment indexing
• Review existing FTS indexes for potentially leaked sensitive content and rebuild if necessary
• Audit system file permissions to minimize exposure in case of similar vulnerabilities

Patch Information

The vendor recommends discontinuing use of the provided attachment conversion script entirely. Instead, administrators should implement alternative solutions such as FTS Tika for secure attachment-to-text conversion. Refer to the Open-Xchange Security Advisory for complete remediation guidance.

No publicly available exploits are known for this vulnerability at this time.

Workarounds

• Replace the vulnerable script with FTS Tika or another secure attachment conversion solution
• Disable OOXML attachment indexing entirely if alternative solutions cannot be immediately deployed
• Implement strict file system permissions to limit what files the indexing process can access
• Configure Dovecot FTS to skip processing of potentially dangerous attachment types until migration is complete

# Configuration example - Disable vulnerable script and switch to Tika
# In dovecot.conf or relevant conf.d file:

# Comment out or remove the vulnerable decode2text script
# plugin {
#   fts_decoder = decode2text
# }

# Enable FTS Tika instead
plugin {
  fts_tika = http://localhost:9998/tika/
}

# Alternatively, disable attachment indexing temporarily
plugin {
  fts_enforced = no
  # fts_decoder = <disabled>
}