CVE-2026-26064

HighPublic PoC

Published: 20 February 2026

Published

20 February 2026

Modified

20 February 2026

KEV Added

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Patch

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CVSS Score 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0008 24.0th percentile

Risk Priority 18 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-26064 is a high-severity Path Traversal (CWE-22) vulnerability in Calibre-Ebook Calibre. Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Malicious File (T1204.002); ranked at the 24.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Malicious File (T1204.002) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match

prevent

Requires validation of ZIP file paths in the extract_pictures function to block path traversal sequences like '..', preventing arbitrary file writes.

SI-2 Flaw Remediation good match

prevent

Mandates timely flaw remediation, including patching calibre to version 9.3.0 or later where proper path sanitization was implemented.

SI-9 Information Input Restrictions partial match

prevent

Enforces restrictions on file path inputs to limit extraction and writes to authorized directories like 'Pictures', mitigating traversal exploits.

MITRE ATT&CK Enterprise TechniquesAI

T1204.002 Malicious File Execution

An adversary may rely upon a user opening a malicious file in order to gain execution.

attack.mitre.org →

T1547.001 Registry Run Keys / Startup Folder Persistence

Adversaries may achieve persistence by adding a program to a startup folder or referencing it with a Registry run key.

attack.mitre.org →

Why these techniques?

Path traversal enables arbitrary file write from malicious e-book/ZIP opened by user (T1204.002); description explicitly notes writing payload to Windows Startup folder for login execution (T1547.001).

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

calibre is a cross-platform e-book manager for viewing, converting, editing, and cataloging e-books. Versions 9.2.1 and below contain a Path Traversal vulnerability that allows arbitrary file writes anywhere the user has write permissions. On Windows, this leads to Remote Code…

Execution by writing a payload to the Startup folder, which executes on next login. Function extract_pictures only checks startswith('Pictures'), and does not sanitize '..' sequences. calibre's own ZipFile.extractall() in utils/zipfile.py does sanitize '..' via _get_targetpath(), but extract_pictures() bypasses this by using manual zf.read() + open(). This issue has been fixed in version 9.3.0.

Deeper analysisAI

CVE-2026-26064 is a path traversal vulnerability (CWE-22) affecting calibre, a cross-platform e-book manager used for viewing, converting, editing, and cataloging e-books. The issue impacts versions 9.2.1 and earlier, stemming from the extract_pictures function, which only checks if paths start with 'Pictures' but fails to sanitize '..' sequences. This allows arbitrary file writes to locations where the user has write permissions. While calibre's custom ZipFile.extractall() in utils/zipfile.py properly sanitizes paths via _get_targetpath(), the extract_pictures function bypasses this protection by manually using zf.read() and open(). The vulnerability carries a CVSS v3.1 base score of 8.8 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) and was published on 2026-02-20.

An attacker can exploit this vulnerability by supplying a malicious e-book or ZIP file that triggers the extract_pictures function, such as during e-book processing. Exploitation requires low privileges (PR:L), is network-accessible with low complexity and no user interaction beyond opening the file in calibre. Successful attacks enable arbitrary file writes in the user's writable directories. On Windows, this facilitates remote code execution by writing a payload to the Startup folder, which executes upon the next user login.

The GitHub security advisory (GHSA-72ch-3hqc-pgmp) and fixing commit (e1b5f9b45a5e8fa96c136963ad9a1d35e6adac62) confirm the issue was resolved in calibre version 9.3.0 through proper path sanitization in extract_pictures. Security practitioners should advise users to update to 9.3.0 or later and avoid processing untrusted e-books until patched.