PatchTheCVECVE-2026-6402: webpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when
CVE-2026-6402 is a medium-severity flaw (CVSS 5.3) affecting webpack-dev-server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
webpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when serving over a non-potentially trustworthy origin such as plain HTTP. The previous fix relied on the Sec-Fetch-Mode and Sec-Fetch-Site request headers, which browsers omit for non-trustworthy origins, allowing a malicious site to load the bundled source as a script and read it across origins. Impact: an attacker controlling a website vis
Why this priority
- No elevated risk signals yet
A fixed release or distro patch exists.
Risk facts
| CVSS score | 5.3 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | High |
| Privileges needed | None |
| User interaction | Required |
| EPSS exploit chance | 0.3% (top 78%) |
| CISA exploited list | No |
| Weakness | CWE-749 |
| Published | 2026-05-12 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-6402?
webpack-dev-server: upgrade to 5.2.4. Exact commands for each OS are on this page.
Is CVE-2026-6402 being exploited?
CVE-2026-6402 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-6402 affect?
CVE-2026-6402 affects webpack-dev-server. Severity is medium (CVSS 5.3). webpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when serving over a non-potentially trustworthy origin such as plain HTTP. The previous fix relied on the Sec-Fetch-Mode and Sec-Fetch
How urgent is CVE-2026-6402?
Priority 24/100. No elevated risk signals yet.
Software pages
Related CVEs
- CVE-2026-14620 MEDIUM 4.7 UPGRADE webpack-dev-server versions 5.2.5 and earlier expose two internal developer endpoints, /webpack-dev-server/ope
- CVE-2026-14631 MEDIUM 5.3 UPGRADE webpack-dev-server versions 5.2.5 and earlier terminate the whole Node.js process when an unauthenticated peer
- CVE-2026-9595 MEDIUM 5.3 UPGRADE Impact: When a user-configured proxy on webpack-dev-server has a broad context (e.g