Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-34745 is a critical-severity Path Traversal (CWE-22) vulnerability in Shaneisrael Fireshare. Its CVSS base score is 9.1 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 48th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and SI-10 (Information Input Validation) — 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-2026-34745 is a path traversal vulnerability (CWE-22) in Fireshare, an open-source self-hosted media and link sharing application. The issue affects versions prior to 1.5.3 and stems from an incomplete fix for the related CVE-2026-33645. While the patch for CVE-2026-33645 was applied to the authenticated /api/uploadChunked endpoint, it was not extended to the unauthenticated /api/uploadChunked/public endpoint in the file app/server/fireshare/api.py. This allows exploitation of the checkSum parameter to write arbitrary files with attacker-controlled content to any writable path on the server filesystem. The vulnerability carries a CVSS v3.1 base score of 9.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H).
An unauthenticated attacker can exploit this vulnerability remotely with low complexity and no user interaction required. By sending crafted requests to the /api/uploadChunked/public endpoint, the attacker can upload chunks of data that bypass path restrictions, enabling arbitrary file writes on the server. Successful exploitation grants high-impact integrity and availability disruption, such as overwriting critical configuration files, scripts, or binaries, potentially leading to full server compromise, though confidentiality is not directly affected.
The vulnerability has been addressed in Fireshare version 1.5.3, as detailed in the project's security advisory (GHSA-fvvp-rj8g-c7gc), release notes, associated pull request #520, and the patching commit b76915607924756e6fa1a5f6c8823c38d611fb24. Security practitioners should upgrade to version 1.5.3 or later and review server filesystem permissions to limit damage from any prior exposures.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-18507
Vulnerability Data
Fireshare facilitates self-hosted media and link sharing. Prior to version 1.5.3, the fix for CVE-2026-33645 was applied to the authenticated /api/uploadChunked endpoint but was not applied to the unauthenticated /api/uploadChunked/public endpoint in the same file (app/server/fireshare/api.py). An unauthenticated attacker can…
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exploit the checkSum parameter to write arbitrary files with attacker-controlled content to any writable path on the server filesystem. This issue has been patched in version 1.5.3.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V5.3.2
Mitigating Controls (NIST 800-53 r5) AI
Enforces the intended directory access authorizations that path traversal would otherwise bypass.
Input validation directly neutralizes special path elements before pathname construction occurs.
Least privilege reduces the impact of any unauthorized file access obtained via traversal.
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.
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.
Secure SDLC mandates input validation and path sanitization that directly prevent path traversal.
Application security requirements include rules for safe file handling and canonicalization.
Secure architecture principles require least-privilege file access and directory isolation.
Secure coding standards explicitly forbid unsafe path construction and mandate safe APIs.
Security testing in development catches path traversal via static/dynamic analysis.
Information access restriction limits which files an application may read or write.