Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:HSummary
CVE-2026-27699 is a critical-severity Path Traversal (CWE-22) vulnerability in Patrickjuchli Basic-Ftp. 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 42th 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-2026-27699 is a path traversal vulnerability (CWE-22) in the `basic-ftp` FTP client library for Node.js, affecting versions prior to 5.2.0. The flaw exists in the `downloadToDir()` method, where a malicious FTP server can send directory listings with filenames containing path traversal sequences such as `../`. This causes downloaded files to be written outside the intended download directory on the client side.
The vulnerability can be exploited by any attacker who controls an FTP server to which a victim application connects using the affected library. Per the CVSS v3.1 base score of 9.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H), exploitation is achievable remotely with low complexity, no privileges, and no user interaction. Attackers can achieve high integrity and availability impacts by writing files to arbitrary locations outside the specified directory on the victim's filesystem.
Mitigation is available in `basic-ftp` version 5.2.0, which patches the issue. Security advisories recommend updating to this version or later. Relevant resources include the GitHub security advisory at https://github.com/patrickjuchli/basic-ftp/security/advisories/GHSA-5rq4-664w-9x2c, release notes at https://github.com/patrickjuchli/basic-ftp/releases/tag/v5.2.0, and the patching commit at https://github.com/patrickjuchli/basic-ftp/commit/2a2a0e6514357b9eda07c2f8afbd3f04727a7cd9.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8643
Vulnerability Data
The `basic-ftp` FTP client library for Node.js contains a path traversal vulnerability (CWE-22) in versions prior to 5.2.0 in the `downloadToDir()` method. A malicious FTP server can send directory listings with filenames containing path traversal sequences (`../`) that cause files…
more
to be written outside the intended download directory. Version 5.2.0 patches the issue.
- 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.
Security testing in development catches path traversal via static/dynamic analysis.
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.
Information access restriction limits which files an application may read or write.