Which versions of Calibre are affected by EUVD-2026-16612?

Calibre versions before 9.6.0 contain a critical file disclosure vulnerability that allows unauthenticated attackers to exfiltrate arbitrary files from affected systems by exploiting path traversal…. A patch is available.

How to fix or mitigate EUVD-2026-16612?

Within 24 hours: Identify all systems running Calibre versions prior to 9.6.0 using asset inventory and network scanning. Within 7 days: Upgrade all instances to Calibre 9.6.0 or later per vendor patch release. Within 30 days: Conduct file access log review for suspicious background-image endpoint requests and audit any systems that may have hosted sensitive files accessible to Calibre processes.

Calibre EUVD-2026-16612

Q: What is the CVSS score of EUVD-2026-16612?

EUVD-2026-16612 has a CVSS 4.0 base score of 8.2 (High). CVSS vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. EPSS exploitation probability: 0.0%.

| CVE-2026-33206 HIGH

Relative Path Traversal (CWE-23)

2026-03-27 GitHub_M

Authentication Bypass Path Traversal SSRF Calibre Kovidgoyal

8.2

CVSS 4.0 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

8.2 HIGH

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

SUSE

HIGH

qualitative

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

Attack Vector

Local

Attack Complexity

Low

Privileges Required

None

User Interaction

Scope

Lifecycle Timeline

Analysis Updated

Apr 16, 2026 - 06:12 EUVD-patch-fix

executive_summary

Re-analysis Queued

Apr 16, 2026 - 05:29 backfill_euvd_patch

patch_released

Patch available

Apr 16, 2026 - 05:29 EUVD

9.6.0

EUVD ID Assigned

Mar 27, 2026 - 14:30 euvd

EUVD-2026-16612

Analysis Generated

Mar 27, 2026 - 14:30 vuln.today

CVE Published

Mar 27, 2026 - 13:53 nvd

HIGH 8.2

DescriptionGitHub Advisory

calibre is a cross-platform e-book manager for viewing, converting, editing, and cataloging e-books. Prior to version 9.6.0, a path traversal vulnerability exists in Calibre' handling of images in Markdown and other similar text-based files allowing an attacker to include arbitrary files from the file system into the converted book. Additionally, missing authentication and server-side request forgery in the background-image endpoint in the ebook reader web view allow the files to be exfiltrated without additional interaction. Version 9.6.0 contains a fix.

AnalysisAI

Calibre versions prior to 9.6.0 allow remote attackers to exfiltrate arbitrary files from the host system through a combination of path traversal in image handling during file conversion and unauthenticated server-side request forgery in the ebook reader web view's background-image endpoint. An attacker can craft a malicious markdown or text-based file that references files outside the intended directory, then retrieve those files through the unprotected background-image handler without authentication, enabling complete file system disclosure on systems running vulnerable Calibre instances.

Technical ContextAI

The vulnerability chain exploits two distinct weaknesses in Calibre (affected CPE: cpe:2.3:a:kovidgoyal:calibre:*:*:*:*:*:*:*:*). First, a path traversal flaw (CWE-23: Relative Path Traversal) in the image handling logic of Calibre's file conversion system fails to properly validate or sanitize file paths when processing embedded images in Markdown and similar text-based formats, allowing directory traversal sequences (e.g., '../../../etc/passwd') to reference files outside the intended working directory. Second, the background-image endpoint in the integrated ebook reader web view lacks both authentication controls and input validation, creating a server-side request forgery (SSRF) condition that permits unauthenticated requests to retrieve arbitrary file URLs. Together, these flaws enable an attacker to convert a malicious document containing path-traversed image references, then exfiltrate the resulting sensitive files via the unprotected background-image endpoint.

RemediationAI

Upgrade Calibre to version 9.6.0 or later immediately, as this version contains the fix for both the path traversal and missing authentication issues. See the vendor security advisory at https://github.com/kovidgoyal/calibre/security/advisories/GHSA-h3p4-m74f-43g6 for patch availability and deployment guidance. As a temporary mitigation prior to patching, disable or restrict network access to the ebook reader web view, disable the background-image endpoint if configurable, and limit file conversion operations to trusted sources only. Additionally, implement network-level access controls to restrict Calibre instances to trusted users and networks, and avoid converting untrusted markdown or text-based documents until the patch is applied.