SB20260629105 - Multiple vulnerabilities in Calibre

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Main Vulnerability Database SB20260629105

SB20260629105 - Multiple vulnerabilities in Calibre

Published: June 29, 2026

Security Bulletin ID SB20260629105
CSH Severity
High
Patch available
YES
Number of vulnerabilities 3
Exploitation vector Remote access
Highest impact Code execution

Breakdown by Severity

High 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 3 vulnerabilities.


1) Improper Neutralization of Special Elements Used in a Template Engine (CVE-ID: CVE-2026-25731)

CWE-ID: CWE-1336 - Improper Neutralization of Special Elements Used in a Template Engine

CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber


The vulnerability allows a remote attacker to execute arbitrary code.

The vulnerability exists due to server-side template injection in the HTML export feature when processing crafted template content during conversion. A remote attacker can embed template expressions in a crafted input to execute arbitrary code.

User interaction is required to open or convert crafted content.


2) Path traversal (CVE-ID: CVE-2026-25635)

CWE-ID: CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber


The vulnerability allows a remote attacker to execute arbitrary code.

The vulnerability exists due to path traversal in src/calibre/ebooks/chm/reader.py when processing a crafted CHM file during conversion. A remote attacker can trick the victim into converting a malicious CHM file to execute arbitrary code.

On Windows, arbitrary file write outside the extraction directory can be leveraged by placing a payload in the Startup folder, which executes on the next login. User interaction is required to convert the crafted CHM file via the GUI or the ebook-convert CLI.


3) Path traversal (CVE-ID: CVE-2026-25636)

CWE-ID: CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber


The vulnerability allows a remote attacker to execute arbitrary code.

The vulnerability exists due to path traversal in file handling when opening a crafted file. A remote attacker can trick the victim into opening a crafted file to execute arbitrary code.

The issue can also lead to arbitrary file corruption. User interaction is required to open a crafted file.


Remediation

Install update from vendor's website.

References