CVE-2025-55780Network attack vector

Renderer crash via malformed right-to-left EPUB

Published Sep 23, 2025 · Updated Sep 23, 2025

NULL pointer dereference in MuPDF 1.26.4 allows remote attackers to crash the renderer with a malformed EPUB document. The break_word_for_overflow_wrap() function can leave node->next null when splitting an oversized right-to-left FLOW_WORD under overflow-wrap: break-word, then dereferences node->next->overflow_wrap. Exploitation requires MuPDF to render the crafted document and interrupts only that application process; no code execution or data compromise is reported.

CVSS severity7.5
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

NULL pointer dereference in MuPDF 1.26.4 allows remote attackers to crash the renderer with a malformed EPUB document. The break_word_for_overflow_wrap() function can leave node->next null when splitting an oversized right-to-left FLOW_WORD under overflow-wrap: break-word, then dereferences node->next->overflow_wrap. Exploitation requires MuPDF to render the crafted document and interrupts only that application process; no code execution or data compromise is reported.

The record

CVE
CVE-2025-55780
Published
Sep 23, 2025
Updated
Sep 23, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 23, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 23, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo