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MupdfApplication · Artifex

CVE-2025-55780

HIGH · 7.5 CVSS v3.1 Published 2025-09-23
Fix available
A fix is available. Upgrade to 1.26.7 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

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
A null pointer dereference occurs in the function break_word_for_overflow_wrap() in MuPDF 1.26.4 when rendering a malformed EPUB document. Specifically, the function calls fz_html_split_flow() to split a FLOW_WORD node, but does not check if node->next is valid before accessing node->next->overflow_wrap, resulting in a crash if the split fails or returns a partial node chain.

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 null pointer dereference vulnerability exists in MuPDF 1.26.4 within the break_word_for_overflow_wrap() function when rendering EPUB documents. The function calls fz_html_split_flow() to split a FLOW_WORD node but fails to validate that node->next exists before accessing node->next->overflow_wrap, causing a crash when the split operation fails or returns an incomplete node chain.

MitigationUpdate MuPDF to the latest patched version. Until an update is available, avoid processing untrusted or malformed EPUB documents with vulnerable versions.

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
MupdfApplication
Affected:>= 1.24.0, < 1.26.7

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
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

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. Determine installed MuPDF version
    Run 'mupdf --version' from command line, or check the shared library file version (libmupdf.so on Linux systems, mupdf.dll on Windows). On Linux also try: dpkg -l | grep mupdf or rpm -qa | grep mupdf
    Affected if Version is 1.24.0, 1.24.1, 1.24.2, 1.24.3, 1.24.4, 1.24.5, 1.25.0 through 1.25.x, 1.26.0 through 1.26.6, or any version >= 1.24.0 and < 1.26.7
  2. Identify if EPUB processing is enabled
    Inspect the application or tool using MuPDF to confirm it supports EPUB format. Check configuration files, plugins, or document type associations for .epub file handling. Look for EPUB-specific modules or the fz_html_split_flow function in any custom integration
    Affected if The tool is configured to render or parse EPUB documents using MuPDF's HTML/EPUB rendering engine
  3. Verify the vulnerable code path can be triggered
    Attempt to process a malformed or specially crafted EPUB file that triggers the overflow wrap code path in break_word_for_overflow_wrap(). Monitor for crashes or null pointer errors during EPUB rendering, particularly when text overflow handling occurs
    Affected if Processing EPUB documents causes the application to call break_word_for_overflow_wrap() on an incomplete node chain from fz_html_split_flow()

Environment is affected if MuPDF version is 1.24.0 or higher but below 1.26.7 AND the software uses MuPDF to render EPUB documents, enabling the vulnerable break_word_for_overflow_wrap() function to be invoked.

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 1.26.7 or later
Fixed in 1.26.7
Interim mitigation

Update MuPDF to the latest patched version. Until an update is available, avoid processing untrusted or malformed EPUB documents with vulnerable versions.

Recommended fix High confidence

MuPDF 1.26.7 or later

  1. Identify all systems and applications using MuPDF versions 1.24.0 through 1.26.6
  2. Upgrade MuPDF to version 1.26.7 or later (the latest stable 1.26.x release recommended)
  3. Verify the upgrade by checking the MuPDF library version
  4. Test EPUB document rendering to confirm the fix resolves the null pointer dereference

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

Fix this in Mupdf Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

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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-2025-55780 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