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CVE-2026-6402· NVD / CVE Program· CNA openjs

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

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 visited by a developer running webpack-dev-server can recover the application source code when the dev server runs over HTTP at a guessable host and port. Chromium based browsers from Chrome 142 onward are not affected due to local network access restrictions. Upgrade to webpack-dev-server 5.2.4 or later, which sets Cross-Origin-Resource-Policy: same-origin on responses.

MediumCVSS 6.5 · v3.1—No exploit Fix available
Published
May 12, 2026
Updated
Jun 17, 2026
EPSS
0.4% · 26th percentile
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Report tools

JSON

Action score

26

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
6.5
CNA · openjs
5.3
1.2 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

VendorProduct
webpack.jswebpack-dev-server

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • webpack.js webpack-dev-serverbefore 5.2.4

Versions reported by the vendor

Affected version ranges reported by the assigning authority (openjs). Independent of NVD's CPE analysis and usually ahead of it.

  • webpack-dev-server webpack-dev-server

    • 5.2.4not affected
    • before 5.2.4affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
npmwebpack-dev-serverbefore 5.2.45.2.4
openSUSE:Tumbleweedagama-web-uibefore 21+360.16caae772-44.121+360.16caae772-44.1

Same product

webpack.js: all records

Other highest-scoring records for the same primary product.

  • CVE-2018-14732An issue was discovered in lib/Server.js in webpack-dev-server before 3.1.6.
    31Monitor
  • CVE-2025-30360webpack-dev-server users' source code may be stolen when they access a malicious web site with non-Chromium based browser
    26Monitor
  • CVE-2025-30359webpack-dev-server users' source code may be stolen when they access a malicious web site
    23Monitor
  • CVE-2026-14631webpack-dev-server vulnerable to denial of service via a malformed Host or Origin header
    21Monitor
  • CVE-2026-14620webpack-dev-server vulnerable to cross-site request forgery via internal developer endpoints
    18Monitor
  • CVE-2026-9595webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies
    17Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
webpack-dev-server webpack-dev-server5.2.4Vendor (CNA)
npm:webpack-dev-server5.2.4Package registry (OSV)
opensuse:agama-web-ui21+360.16caae772-44.1 · openSUSE:TumbleweedPackage registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2025-30359343 days apartwebpack-dev-server users' source code may be stolen when they access a malicious web site
    23Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
none
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality impact
High
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-749 · Exposed Dangerous Method or Function

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

—

Noroxi analysis

No Noroxi analysis for this record yet

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Change log

  1. Fix✗ → ✓

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References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records