CVE-2026-25635Public exploit

Code execution via unsanitized CHM extraction paths

Published Feb 6, 2026 · Updated Feb 6, 2026

Path traversal in calibre's CHM reader before 9.2.0 allows attackers to write files through a crafted CHM archive. The reader strips only a leading slash from archive paths, leaves .. sequences intact, joins them to the extraction directory, and writes attacker-controlled content outside it. A user must convert the malicious file; on Windows, a Startup-folder write executes the payload at the next login.

CVSS severity8.6
High
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in calibre's CHM reader before 9.2.0 allows attackers to write files through a crafted CHM archive. The reader strips only a leading slash from archive paths, leaves .. sequences intact, joins them to the extraction directory, and writes attacker-controlled content outside it. A user must convert the malicious file; on Windows, a Startup-folder write executes the payload at the next login.

The record

CVE
CVE-2026-25635
Published
Feb 6, 2026
Updated
Feb 6, 2026
Vendor
Kovid Goyal
Product
calibre
Classifications
CWE-22, T1204.002, T1547.001
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 6, 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=< 9.2.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Kovid Goyal · calibreversion=< 9.2.0

Published CVSS scores

8.6GitHub, Inc.CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1204.002User Execution: Malicious File
T1547.001Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder

Public exploit references

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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