Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:HSummary
CVE-2026-35031 is a critical-severity Improper Input Validation (CWE-20) vulnerability in Jellyfin Jellyfin. Its CVSS base score is 9.9 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 48% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and SA-11 (Developer Testing and Evaluation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-35031 affects Jellyfin, an open-source self-hosted media server, in versions prior to 10.11.7. The vulnerability is a chain rooted in the subtitle upload endpoint (POST /Videos/{itemId}/Subtitles), where the Format field lacks validation. This enables path traversal through the file extension, resulting in arbitrary file writes. Associated CWEs include CWE-20 (Improper Input Validation), CWE-22 (Path Traversal), and CWE-187 (Incomplete Blacklist). The issue carries a CVSS v3.1 score of 9.9 (AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H).
Exploitation requires an administrator account or a user explicitly granted the "Upload Subtitles" permission. Attackers can leverage the initial arbitrary file write to chain into arbitrary file reads using .strm files, extract the database, escalate to admin privileges, and achieve remote code execution as root via ld.so.preload.
The vulnerability has been addressed in Jellyfin version 10.11.7. For those unable to upgrade immediately, the advisory recommends granting non-administrator users the Subtitle upload permission to minimize the attack surface. Additional details are available in the release notes at https://github.com/jellyfin/jellyfin/releases/tag/v10.11.7 and the security advisory at https://github.com/jellyfin/jellyfin/security/advisories/GHSA-j2hf-x4q5-47j3.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-22764
Vulnerability Data
Jellyfin is an open source self hosted media server. Versions prior to 10.11.7 contain a vulnerability chain in the subtitle upload endpoint (POST /Videos/{itemId}/Subtitles), where the Format field is not validated, allowing path traversal via the file extension and enabling…
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arbitrary file write. This arbitrary file write can be chained into arbitrary file read via .strm files, database extraction, admin privilege escalation, and ultimately remote code execution as root via ld.so.preload. Exploitation requires an administrator account or a user that has been explicitly granted the "Upload Subtitles" permission. This issue has been fixed in version 10.11.7. If users are unable to upgrade immediately, they can grant non-administrator users Subtitle upload permissions to reduce attack surface.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 6 hardening rules · 3 OS baselines
V10.4.1V5.3.2
Mitigating Controls (NIST 800-53 r5) AI
Enforces the intended directory access authorizations that path traversal would otherwise bypass.
Developer testing and evaluation can discover missing input validation through analysis or test cases.
SI-10 directly requires validity checks on information inputs, structurally preventing improper or missing validation.
Least privilege reduces the impact of any unauthorized file access obtained via traversal.
Requiring documented development standards and tools can embed input-validation practices into the engineering process.
Security engineering principles include correct and complete comparison logic to avoid flawed decision points.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require and enforce input validation during development.
Vulnerability identification processes can discover partial-comparison flaws during code or binary analysis.
Patching/maintenance can remediate known path-traversal flaws in deployed software (partial prevention of exploitability) but does nothing to stop the coding defect from being introduced in the first place.
PR.AA-05 defines and reviews access policies but does not address code-level pathname neutralization, so neither direction prevents CWE-22.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Testing against a defined set of requirements and using code review plus vulnerability scanning forces validation of inputs and handling of unanticipated conditions, reducing the chance that malformed data will be accepted.
Secure-coding guidelines and mandatory security testing (including code scans) compel developers to validate and sanitize inputs at design and implementation time, lowering the incidence of malformed or malicious data reaching downstream components.
Mandating input controls that include integrity checks and input validation ensures that untrusted data is examined before use, blocking the root cause of many injection and malformed-data weaknesses.
Security-by-design principles explicitly call for data validation and sanitization at every layer, reducing the chance that malformed or malicious input will be processed without scrutiny.
Requiring language-specific secure coding standards, peer review, SAST and documented mitigation of common programming errors forces validation of all inputs before they are trusted.
Information access restriction limits which files an application may read or write.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
RHEL 8 (1 rule)
- V-230265 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-20