VulnerabilityPublished 26 Jun 2026

better-helperjs Vulnerable to Directory Traversal via String Prefix Bypass in Static Server

Affects better-helperjsSource GCVE Database

CVSS 7.5 High : upgrade to 3.0.6 soon.

Data as of 26 Jun 2026, 22:06 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 3.0.6

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

What to do

Upgrade better-helperjs to 3.0.6.

Affected software

Product	Affected	Fixed in
npmbetter-helperjs	Affected <3.0.6	Fixed in 3.0.6

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AI-suggested

An official patch is available in better-helperjs version 3.0.6 and later, which fixes the path validation logic to prevent prefix-based directory traversal. Users should upgrade to version 3.0.6 or newer. If upgrading is not immediately possible, users should ensure that no sensitive directories with names sharing the static root directory's prefix are deployed adjacent to the static files directory to mitigate the risk.

Description

A directory traversal vulnerability exists in better-helperjs static file server versions up to 3.0.5. The vulnerability arises from improper path validation using string prefix checks, allowing attackers to access files in adjacent directories with names sharing the static root directory's prefix. This flaw enables unauthorized reading of sensitive files outside the intended public directory. The issue is fixed in version 3.0.6 by enforcing exact path boundary checks. No known exploits are reported in the wild.

Impact

An attacker can read arbitrary files located in directories adjacent to the static root directory if those directories share the same string prefix as the root. This leads to unauthorized disclosure of potentially sensitive information. The vulnerability has a CVSS 3.1 base score of 7.5 (High) with network attack vector, no privileges required, and no user interaction needed. There is no impact on integrity or availability.

Summary

better-helperjs versions <= 3.0.5 contain a directory traversal vulnerability in the production static file server. The vulnerability is due to the use of String.prototype.startsWith() to validate requested paths against the static root directory, which is insufficient because it only checks string prefixes rather than actual directory boundaries. An attacker can exploit this by requesting files in adjacent directories whose names start with the static root directory's prefix, bypassing the validation and reading arbitrary files. The flaw is corrected in version 3.0.6 by requiring the resolved path to start with the root directory plus a path separator or be exactly the root directory, preventing prefix-based bypasses.

CWE-22Improper Limitation of a Pathname to a Restricted Directory (Path Traversal) (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #6OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
Implementation · Input Validation
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.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
Implementation · Input Validation
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).
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.3.1 (opens in a new tab)
Attack patterns
Path Traversal (opens in a new tab)
Using Slashes and URL Encoding Combined to Bypass Validation Logic (opens in a new tab)
Manipulating Web Input to File System Calls (opens in a new tab)
Using Escaped Slashes in Alternate Encoding (opens in a new tab)
Using Slashes in Alternate Encoding (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Jun 2026, 22:06 UTC

WeaknessesCWE-22

Technical details

References

Community reviews

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