Security readout for executives and security teams
Plain-English summary
calibre Content Server versions before 9.4.0 can let a logged-in user manipulate HTTP response headers. This could affect how browsers handle server responses, with limited confidentiality and integrity impact. The issue matters most where calibre Content Server is exposed to untrusted authenticated users.
Executive priority
Treat as a moderate-priority patching item. Prioritize internet-reachable or broadly shared calibre Content Server deployments. There is a vendor fix, but no provided evidence of active exploitation.
Technical view
CVE-2026-27810 is a CWE-113 HTTP response header injection flaw in calibre Content Server before 9.4.0. The unsanitized `content_disposition` query parameter affects `/get/` and `/data-files/get/` endpoints. Exploitation requires authentication, or an authenticated victim clicking a crafted link. CVSS 3.1 score is 6.4.
Likely exposure
Systems running calibre Content Server below version 9.4.0 with authentication enabled are affected. Exposure is higher when authenticated access is available to many users or reachable over the network.
Exploitation context
The source states any authenticated user can exploit the issue, and it may be triggered by tricking an authenticated victim into clicking a crafted link. No provided source indicates active exploitation or CISA KEV listing.
Researcher notes
Evidence is limited to the CVE record and GitHub advisory. The affected condition is specific: calibre Content Server before 9.4.0 with authentication enabled. Avoid assuming impact beyond HTTP response header injection unless vendor guidance adds details.
Mitigation direction
- Upgrade calibre to version 9.4.0 or later.
- Review vendor advisory GHSA-5fpj-fxw7-8grw for current guidance.
- Limit calibre Content Server access to trusted users and networks where feasible.
Validation and detection
- Inventory calibre Content Server instances and record versions.
- Confirm whether authentication is enabled on each Content Server.
- Flag any Content Server running calibre below 9.4.0.
- Review access logs for unusual requests to affected endpoints, without relying on this as proof.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-113: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-27810 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N3.12.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.4MediumVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/kovidgoyal/calibre/security/advisories/GHSA-5fpj-fxw7-8grwCVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.