How severe is CVE-2026-27810?

CVE-2026-27810 has a CVSS 3.x base score of 6.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-27810 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-27810?

CVE-2026-27810 affects Calibre-ebook Calibre. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-27810?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-27810 have an EU (EUVD) identifier?

Yes. CVE-2026-27810 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-9056.

When was CVE-2026-27810 published?

CVE-2026-27810 was published on 2026-02-27 and last updated on 2026-06-17.

CVE-2026-27810

CVE-2026-27810 is a medium-severity vulnerability in Calibre-ebook Calibre with a CVSS 3.x base score of 6.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-113.

Key facts

Severity: Medium (CVSS 3.x base score 6.4)
EPSS exploit prediction: 0% (11th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-9056
Weakness: CWE-113
Affected product: Calibre-ebook Calibre
Published: 2026-02-27
Last modified: 2026-06-17

Description

calibre is a cross-platform e-book manager for viewing, converting, editing, and cataloging e-books. Prior to version 9.4.0, an HTTP Response Header Injection vulnerability in the calibre Content Server allows any authenticated user to inject arbitrary HTTP headers into server responses via an unsanitized `content_disposition` query parameter in the `/get/` and `/data-files/get/` endpoints. All users running the calibre Content Server with authentication enabled are affected. The vulnerability is exploitable by any authenticated user and can also be triggered by tricking an authenticated victim into clicking a crafted link. Version 9.4.0 contains a fix for the issue.

Frequently asked questions

What is CVE-2026-27810?: calibre is a cross-platform e-book manager for viewing, converting, editing, and cataloging e-books. Prior to version 9.4.0, an HTTP Response Header Injection vulnerability in the calibre Content Server allows any authenticated user to inject arbitrary HTTP headers into server responses via an unsanitized `content_disposition` query parameter in the `/get/` and `/data-files/get/` endpoints. All users running the calibre Content Server with authentication enabled are affected. The vulnerability is exploitable by any authenticated user and can also be triggered by tricking an authenticated victim into clicking a crafted link. Version 9.4.0 contains a fix for the issue.
How severe is CVE-2026-27810?: CVE-2026-27810 has a CVSS 3.x base score of 6.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-27810 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-27810?: CVE-2026-27810 affects Calibre-ebook Calibre. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-27810?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-27810 have an EU (EUVD) identifier?: Yes. CVE-2026-27810 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-9056.
When was CVE-2026-27810 published?: CVE-2026-27810 was published on 2026-02-27 and last updated on 2026-06-17.

References

https://github.com/kovidgoyal/calibre/security/advisories/GHSA-5fpj-fxw7-8grw

Affected products (1)

cpe:2.3:a:calibre-ebook:calibre:*:*:*:*:*:*:*:*

More vulnerabilities in Calibre-ebook Calibre

CVE-2011-4125 — Critical (CVSS 9.8): A untrusted search path issue was found in Calibre at devices/linux_mount_helper.c leading to the ability of…
CVE-2011-4124 — Critical (CVSS 9.8): Input validation issues were found in Calibre at devices/linux_mount_helper.c which can lead to argument injection and…
CVE-2026-26065 — High (CVSS 8.8): calibre is a cross-platform e-book manager for viewing, converting, editing, and cataloging e-books. Versions 9.2.1 and…
CVE-2026-26064 — High (CVSS 8.8): calibre is a cross-platform e-book manager for viewing, converting, editing, and cataloging e-books. Versions 9.2.1 and…
CVE-2026-25635 — High (CVSS 8.6): calibre is an e-book manager. Prior to 9.2.0, Calibre's CHM reader contains a path traversal vulnerability that allows…
CVE-2026-25636 — High (CVSS 8.2): calibre is an e-book manager. In 9.1.0 and earlier, a path traversal vulnerability in Calibre's EPUB conversion allows…

All CVEs affecting Calibre-ebook Calibre →

Other CWE-113 (HTTP Response Splitting) vulnerabilities

CVE-2026-38967 — Critical (CVSS 9.8): CrowCpp Crow through v1.3.1 HTTP is vulnerable to response header injection via unvalidated response header values.
CVE-2026-34520 — Critical (CVSS 9.1): AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, the C parser…
CVE-2025-53007 — High (CVSS 8.9): arduino-esp32 provides an Arduino core for the ESP32. Versions prior to 3.3.0-RC1 and 3.2.1 contain a HTTP Response…
CVE-2024-52875 — High (CVSS 8.8): An issue was discovered in GFI Kerio Control 9.2.5 through 9.4.5. The dest GET parameter passed to the…
CVE-2018-0689 — High (CVSS 8.8): HTTP header injection vulnerability in SEIKO EPSON printers and scanners (DS-570W firmware versions released prior to…
CVE-2018-11347 — High (CVSS 8.8): The YunoHost 2.7.2 through 2.7.14 web application is affected by one HTTP Response Header Injection. This flaw allows…

Browse all CWE-113 (HTTP Response Splitting) vulnerabilities →