Calibre
CVE-2026-25635
HIGH
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessOpen malicious CHM file in Calibre
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ExploitPath traversal writes payload to Windows Startup folder
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ExecutionPayload executes on next user login
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ImpactRemote code execution as user
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V5 - File Handling Path canonicalization, traversal prevention
MITRE ATT&CK
2 techniques across 2 tactics: Discovery, Collection The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | Calibre versions prior to 9.2.0 with CHM reader module enabled. User must open attacker-supplied CHM file. Windows OS required for Startup folder RCE vector. Write permissions to user's Startup directory (default configuration). |
| Impact | CVSS 8.6 (HIGH). Attack vector: Local. Complexity: Low. Privileges required: None. User interaction: Required. Exploitable via remote/network. Public exploit/POC available. |
| Exploit ScenarioDerived | A remote attacker could exploit this vulnerability to Remote Code Execution by writing a payload to the Startup folder, which executes. |
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Alert meAnalysisAIv1 – Mar 12, 2026
Remote code execution in Calibre prior to version 9.2.0 through a path traversal flaw in the CHM reader allows local attackers to write arbitrary files with user permissions, enabling payload execution via the Windows Startup folder. Public exploit code exists for this vulnerability. Windows users should upgrade to Calibre 9.2.0 or later to remediate the risk.
Earlier versions of this analysis (1)
calibre is an e-book manager. Prior to 9.2.0, Calibre's CHM reader contains a path traversal vulnerability that allows arbitrary file writes anywhere the user has write permissions. [CVSS 8.6 HIGH]
RemediationAI
A vendor patch is available — apply it immediately. Fixed in version 9.2.0.. Validate and sanitize file path inputs. Use allowlists.
Affects your stack
Find out whether the stacks and servers you run are on an affected version.
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
Classified as CWE-22 (Path Traversal). Affects Calibre. calibre is an e-book manager. Prior to 9.2.0, Calibre's CHM reader contains a path traversal vulnerability that allows arbitrary file writes anywhere the user has write permissions. On Windows (haven't tested on other OS's), this can lead to Remote Code Execution by writing a payload to the Startup folder, which executes on next login. This vulnerability is fixed in 9.2.0.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Primary rating from GitHub Advisory.
CVSS VectorGitHub Advisory
Lifecycle Timeline
3DescriptionGitHub Advisory
calibre is an e-book manager. Prior to 9.2.0, Calibre's CHM reader contains a path traversal vulnerability that allows arbitrary file writes anywhere the user has write permissions. On Windows (haven't tested on other OS's), this can lead to Remote Code Execution by writing a payload to the Startup folder, which executes on next login. This vulnerability is fixed in 9.2.0.
Executive ViewAI
Calibre versions prior to 9.2.0 contain a critical vulnerability in the CHM reader that enables attackers to write arbitrary files to systems where users have access permissions. Any organization using Calibre for e-book management faces immediate risk of system compromise, data manipulation, and potential lateral movement if the vulnerability is exploited.
Apply vendor patch. If immediate patching is not possible: disable CHM reader functionality in Calibre settings; restrict Calibre access to trusted internal networks only; implement file integrity monitoring on directories where Calibre has write access; restrict user write permissions to critical directories; disable Calibre for non-essential users pending patch deployment.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Path traversal exploits occur when applications use user-controlled input to construct file system paths without proper validation.
Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.
Affected Products (CPE)GitHub Advisory
Remote code execution in Calibre 9.2.1 and earlier allows authenticated users to write arbitrary files via a path traver
Calibre versions 9.2.1 and below allow authenticated users to write arbitrary files with any extension to any writable l
Calibre 9.1.0 and earlier contains a path traversal vulnerability in EPUB conversion that allows malicious EPUB files to
calibre is an e-book manager. [CVSS 7.8 HIGH]
gui2/viewer/bookmarkmanager.py in Calibre 3.18 calls cPickle.load on imported bookmark data, which allows remote attacke
Path traversal in Calibre <= 7.14.0 allow unauthenticated attackers to achieve arbitrary file read. Rated high severity
link_to_local_path in ebooks/conversion/plugins/html_input.py in calibre before 6.19.0 can, by default, add resources ou
calibre before 5.32.0 contains a regular expression that is vulnerable to ReDoS (Regular Expression Denial of Service) i
Unsanitized user-input in Calibre <= 7.15.0 allow users with permissions to perform full-text searches to achieve SQL in
HTTP response header injection in Calibre Content Server prior to version 9.4.0 permits authenticated users to inject ar
Unsanitized user-input in Calibre <= 7.15.0 allow attackers to perform reflected cross-site scripting. Rated medium seve
The E-book viewer in calibre before 2.75 allows remote attackers to read arbitrary files via a crafted epub file with Ja
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