Path Traversal

Cybersecurity 12 Sep 2026 7 min read

Archive Extraction Is a Filesystem Security Boundary

Archive Extraction Is a Filesystem Security Boundary An archive extractor can receive a destination directory, join each stored name beneath it, and still write somewhere else. The gap appears when archive metadata is treated as harmless naming information even though extraction ultimately asks a filesystem to resolve paths, links, and object types with its own semantics. The familiar ../ traversal is only the most visible form of the problem. Absolute paths, symbolic links, hard links, platform-specific path syntax, pre-existing filesystem objects, and replacement races can all affect where a write lands. A robust design therefore cannot reduce extraction safety to a string check performed once before files are created.

Cybersecurity File Security

Cybersecurity 11 Sep 2026 7 min read

Secure Archive Extraction Against Path Traversal

Archive extraction looks simple: open a ZIP or TAR file, iterate over its entries, and write each entry under a destination directory. The dangerous detail is that archive entries carry names and, in some formats, filesystem object types. Those fields come from the archive creator. If extraction code joins an untrusted entry name to a trusted destination without enforcing containment, an entry such as ../../app/config.json can escape the intended directory. A crafted archive can then overwrite files that the application account is permitted to modify.

Cybersecurity Secure Coding

Cybersecurity 05 Sep 2026 9 min read

Keep Untrusted Paths Inside an Intended Directory

Applications often need to turn input into a file operation: download a report, store an attachment, load a template, or unpack an archive. A dangerous mistake is treating an input path as if it were only a name. Paths contain structure, and that structure can redirect the operation somewhere the application did not intend. If an application expects a file under one directory but lets untrusted input influence the resolved location, a path traversal flaw can expose or overwrite files outside that directory. The consequence depends on what the process can access: configuration, application data, credentials, or other users’ files may fall within reach.

Cybersecurity Secure Coding

Cybersecurity 04 Sep 2026 11 min read

Keep File Access Inside an Intended Directory

Applications often let a caller identify a file: download an invoice, open an exported report, read a template, or retrieve an uploaded document. The dangerous version of this design treats a caller-controlled path as if it were already a permitted file. A path can describe movement through a filesystem, not just a filename. If untrusted input is combined with an application directory without a reliable containment check, the resulting path may resolve somewhere outside that directory. A read operation can expose configuration or private data; a write or delete operation can have more serious consequences.

Cybersecurity Secure Coding