CWE-23: Relative Path Traversal

The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory.

Consequences

• Integrity, Confidentiality, Availability: Execute Unauthorized Code or Commands
• Integrity: Modify Files or Directories
• Confidentiality: Read Files or Directories
• Availability: DoS: Crash, Exit, or Restart

How to prevent it

• Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. When validating filenames, use stringent allowlists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a list of allowable file extensions, which will help to avoid CWE-434. Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a denylist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would b
• Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked. Use a built-in path canonicalization function (such as realpath() in C) that produces the canonical version of the pathname, which effectively removes ".." sequences and symbolic links (CWE-23, CWE-59). This includes: realpath() in C getCanonicalPath() in Java GetFullPath() in ASP.NET realpath() or abs_path() in Perl realpath() in PHP
• Operation: Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].

Recent advisories

• CVE-2026-76519 — A vulnerability in the Advanced Malware Protection (AMP) feature of Cisco Secure Email Gateway could allow an unauthenticated, remote attacker to write…
• EEF-CVE-2026-66881 — Path traversal in imported file_entries name allows arbitrary file write via URL-type entry download
• GHSA-83xp-526h-j3ww — File Browser: Archive builder turns backslash filenames into path traversal (zip-slip)
• GHSA-c6f4-wj38-m3g3 — Snipe-IT vulnerable to directory traversal in displaySig
• GHSA-275h-v5h9-vr82 — Siyuan: Authenticated path traversal in /snippets/ static handler (serveSnippets) leaks conf/conf.json secrets and siyuan.db
• GHSA-hwx4-2j3j-g496 — pnpm: Transitive dependency alias path traversal allows project path override via symlink replacement
• GHSA-p4m3-mgmm-c664 — SiYuan: Path Traversal via Double URL Encoding in /assets/*path (publish mode arbitrary file─read), Incomplete fix of CVE-2026-41894
• GHSA-c39w-43gm-34h5 — Gogs has Path Traversal in organization name that results in RCE through Git hooks
• GHSA-645j-cm4x-3xvw — Concrete CMS Vulnerable to Relative Path Traversal
• CVE-2026-34926 — A directory traversal vulnerability in the Apex One (on-premise) server could allow a pre-authenticated local attacker to modify a key table on the server to…
• GHSA-4jvx-93h3-f45h — OpenC3 COSMOS allows arbitrary writes to plugins directory via path-traversed config filenames
• GHSA-66r7-m7xm-v49h — OpenClaw: QQBot media tags could read arbitrary local files through reply text
• GHSA-558g-h753-6m33 — Weblate: Remote code execution during backup restoration
• GHSA-4ph2-f6pf-79wv — PraisonAI Has Arbitrary File Write (Zip Slip) in Templates Extraction
• GHSA-6px9-j4qr-xfjw — pyLoad has an Arbitrary File Write via Path Traversal in edit_package()

All advisories for CWE-23