webpack-dev-server vulnerable to cross-origin source code exposure on non-HTTPS origins

CVE-2026-6402 → View on GitHub ↗ View on CVE.org ↗ View on NVD ↗

Description

Impact

When webpack-dev-server is running on a non-HTTPS origin (the default), cross-origin requests from malicious websites can load the dev server's JavaScript bundles via <script> tags. The fix introduced in v5.2.1 (CVE-2025-30359) relied on Sec-Fetch-Mode and Sec-Fetch-Site request headers to block these requests, but browsers only send these headers for potentially trustworthy origins. Over plain HTTP, the headers are absent and the check is bypassed.

An attacker who knows the dev server's host, port, and output path can exfiltrate all module source code by intercepting the webpack runtime's module registration.

This does not affect Chrome 142+ (and other Chromium-based browsers) due to local network access restrictions.

Patches

Patched in webpack-dev-server >= 5.2.4 by setting Cross-Origin-Resource-Policy: same-origin on responses.

Workarounds

Run the dev server with HTTPS enabled (--https or server.type: 'https' in config).

Resources

Basic information

Type
reviewed
Severity
medium
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2026-05-18 13:31:42 UTC
Updated
2026-05-18 13:31:44 UTC
GitHub reviewed
2026-05-18 13:31:42 UTC
NVD published
2026-05-12

EPSS Score

Score Percentile
0.03% 9.52%

CVSS Scores

Base score Version Severity Vector
5.3 3.1 —
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.

Identifiers

Type Value
GHSA GHSA-79cf-xcqc-c78w ↗
CVE CVE-2026-6402 ↗

CWEs

CWE id Name
CWE-749 Exposed Dangerous Method or Function

Credits

  • sapphi-red (reporter)
  • UlisesGascon (remediation_developer)
  • bjohansebas (remediation_developer)
  • alexander-akait (remediation_reviewer)

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
npm webpack-dev-server <= 5.2.3 5.2.4 —

References

cvelogic Threat Intelligence