CVE-2026-25920Public exploit

Application crash via undersized HuffDic bounds check

Published Feb 9, 2026 · Updated Feb 9, 2026

Heap out-of-bounds read in SumatraPDF 3.5.2 and earlier allows attackers to crash the application by opening a crafted MOBI file. AddCdicData() validates only 1 << codeLength bytes, while DecodeOne() indexes two-byte entries through code * 2 and can read nearly that range past the CDIC dictionary buffer. Exploitation requires a user to open the file and interrupts only the SumatraPDF process; no confidentiality or integrity impact is reported.

CVSS severity5.5
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap out-of-bounds read in SumatraPDF 3.5.2 and earlier allows attackers to crash the application by opening a crafted MOBI file. AddCdicData() validates only 1 << codeLength bytes, while DecodeOne() indexes two-byte entries through code * 2 and can read nearly that range past the CDIC dictionary buffer. Exploitation requires a user to open the file and interrupts only the SumatraPDF process; no confidentiality or integrity impact is reported.

The record

CVE
CVE-2026-25920
Published
Feb 9, 2026
Updated
Feb 9, 2026
Vendor
SumatraPDF
Product
SumatraPDF
Classifications
CWE-125, T1204.002, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=<= 3.5.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

SumatraPDF · SumatraPDFversion=<= 3.5.2

Published CVSS scores

5.5GitHub, Inc.CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1204.002Malicious File
T1499.004Application or System Exploitation

Public exploit references

  • poc.zipproof of concept · unverified

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

Technologies

Your stack

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Your stack

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