CVE-2026-109375: Improper Link Resolution Before File Access ('Link Following') in Vercel deepsec

CVE-2026-109375 is a link following vulnerability in Vercel deepsec prior to version 1.1.17. The issue exists in the extractTarballLocally function, which improperly resolves symbolic or hard links contained in tarballs extracted locally. This allows sandboxed code, which should be isolated, to escape the sandbox by writing files to arbitrary locations on the host system. The vulnerability affects versions >=0.1.0 and <1.1.17. There is no explicit patch link or vendor advisory provided in the input data.

An attacker with control over sandboxed code can leverage this vulnerability to write arbitrary files on the orchestrator host outside the sandbox boundary. This could lead to unauthorized file modification or code execution depending on the environment and usage context. The CVSS score of 4.9 indicates a medium severity impact with network attack vector and low attack complexity but requiring partial user interaction.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official patch or fix information is provided, users should monitor Vercel's advisories for updates. Until a fix is available, avoid running untrusted or prompt-injected code in sandboxed environments using affected versions of deepsec.