Calibre’s image handling in Markdown and similar text files contains a path‑traversal flaw that lets an attacker specify an arbitrary local file to be copied into the converted book. The application therefore can read and package files from any location the attacker can reference. Additionally, the background‑image endpoint of the ebook reader web view lacks authentication and is vulnerable to server‑side request forgery, enabling the same local files to be exfiltrated without extra interaction. The weakness corresponds to CWE‑23 and results in the disclosure of potentially sensitive data on the host system.

All builds of Calibre produced by Kovid Goyal with a version lower than 9.6.0 are susceptible. The software is cross‑platform, operating on Windows, macOS and Linux, and is used for viewing, converting, editing, and cataloging e‑books. Any user who opens or converts a maliciously crafted Markdown or other text based file, or who allows the web view to access the background‑image endpoint on a vulnerable installation, is at risk.

The vulnerability carries a CVSS score of 8.2, placing it in the High severity range, and an EPSS score of less than 1 %, indicating that automated exploitation is unlikely. It is not listed in the CISA Known Exploited Vulnerabilities catalog. Based on the description, it is inferred that the primary attack vector is local or requires the victim to open a specially crafted file; a remote attacker could also abuse the unauthenticated background‑image endpoint if they can trigger it from a web view on the target. The risk is therefore higher for environments where users routinely process untrusted e‑book files or where the background image endpoint is exposed.