Cyber Resilience

CVE-2026-9595

Webpack.Js Webpack-Dev-Server ≤ 5.2.5

Published
15 June 2026
Modified
17 June 2026
Patch / advisory
View advisory
CVSS Score v3.1 5.3
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
EPSS Score 0.0016 6th percentile
Risk Priority 42 floored blend · peak EPSS

Summary

CVE-2026-9595 is a medium-severity Origin Validation Error (CWE-346) vulnerability in Webpack.Js Webpack-Dev-Server. Its CVSS base score is 5.3 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique DHCP Spoofing (T1557.003); ranked at the 6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to AC-16 (Security and Privacy Attributes) and AC-4 (Information Flow Enforcement) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A01:2025 Broken Access ControlA07:2025 Authentication Failures

EU & UK References

Vulnerability Data

Impact: When a user-configured proxy on webpack-dev-server has a broad context (e.g. /) and ws: true, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and Origin header…

more

to the backend, bypasses the dev server's Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket). Patches: Fixed in webpack-dev-server@5.2.5. Workarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required.

CWE(s)
CWE-346CWE-441

Related Threats

MITRE ATT&CK Enterprise Techniques

T1557.003 DHCP Spoofing Credential Access
Adversaries may redirect network traffic to adversary-owned systems by spoofing Dynamic Host Configuration Protocol (DHCP) traffic and acting as a malicious DHCP server on the victim network.
attack.mitre.org →
T1090 Proxy Command And Control
Adversaries may use a connection proxy to direct network traffic between systems or act as an intermediary for network communications to a command and control server to avoid direct connections to their infrastructure.
attack.mitre.org →
T1090.002 External Proxy Command And Control
Adversaries may use an external proxy to act as an intermediary for network communications to a command and control server to avoid direct connections to their infrastructure.
attack.mitre.org →
T1557 Adversary-in-the-Middle Credential Access
Adversaries may attempt to position themselves between two or more networked devices using an adversary-in-the-middle (AiTM) technique to support follow-on behaviors such as [Network Sniffing](https://attack.
attack.mitre.org →
T1557.001 Name Resolution Poisoning and SMB Relay Credential Access
By responding to LLMNR/NBT-NS/mDNS network traffic, adversaries may spoof an authoritative source for name resolution to force communication with an adversary controlled system.
attack.mitre.org →
T1557.002 ARP Cache Poisoning Credential Access
Adversaries may poison Address Resolution Protocol (ARP) caches to position themselves between the communication of two or more networked devices.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-30360Same product: Webpack.Js Webpack-Dev-Server
CVE-2025-30359Same product: Webpack.Js Webpack-Dev-Server
CVE-2026-6402Same product: Webpack.Js Webpack-Dev-Server
CVE-2026-14620Same product: Webpack.Js Webpack-Dev-Server
CVE-2026-14631Same product: Webpack.Js Webpack-Dev-Server
CVE-2025-25306Shared CWE-346, CWE-441
CVE-2025-68157Same vendor: Webpack.Js
CVE-2024-29180Same vendor: Webpack.Js
CVE-2025-68458Same vendor: Webpack.Js
CVE-2024-43788Same vendor: Webpack.Js

Affected Assets

webpack.js
webpack-dev-server
≤ 5.2.5

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 3 hardening rules · 1 OS baseline
Validate
Prove the fix (OWASP ASVS)
  • V3.2.1
  • V3.5.1
  • V3.5.3
  • V3.5.8

Mitigating Controls (NIST 800-53 r5) AI

AC-16 Security and Privacy Attributes good match

Associating and preserving security attributes such as original source identity prevents the loss of provenance that creates the confused deputy.

AC-4 Information Flow Enforcement good match

Information flow enforcement directly requires validating the source of data before allowing transmission or receipt.

IA-3 Device Identification and Authentication good match

Device identification and authentication mandates verifying the source before establishing connections.

SC-23 Session Authenticity good match

Session authenticity mechanisms require validation that communications originate from the expected party.

AC-3 Access Enforcement partial match

Access enforcement directly stops a component from acting on forwarded requests without verifying original source authorizations.

SC-7 Boundary Protection partial match

Boundary protection at interfaces enforces checks on the origin of incoming communications.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.AA-03 mostly match
prevents

Authentication directly verifies the source of users/services/hardware, mitigating origin validation failures.

PR.AA-04 mostly match
prevents

Verifying identity assertions enforces origin validation for conveyed claims.

ID.AM-03 partial match
prevents

Documenting authorized flows supports origin validation by defining expected sources.

PR.AA-05 partial match
prevents

Enforcing least-privilege authorizations on forwarded requests reduces confused-deputy abuse even if source identity is lost.

PR.IR-01 partial match
prevents

Protecting networks from unauthorized access requires origin checks on communication sources.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.15 Access control partial match
prevents

Access-control rules can limit which upstream identities may cause the product to act on their behalf, reducing confused-deputy risk.

A.5.16 Identity management partial match
prevents

Proper identity management ensures the original requester identity is preserved and validated before the product forwards requests.

A.5.18 Access rights partial match
degrades

Explicit access-rights assignment can restrict the product’s ability to act as an unintended proxy for external actors.

A.8.2 Privileged access rights partial match
degrades

Privileged-access controls limit the rights the product may exercise on behalf of upstream callers, mitigating confused-deputy abuse.

A.8.20 Networks security partial match
mitigates

Network security controls enforce origin validation at network boundaries.

A.8.21 Security of network services partial match
mitigates

Security of network services includes validating the authenticity of service endpoints.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).

Oracle Linux 8 (3 rules)
  • V-248574 YUM must be configured to prevent the installation of patches, service packs, device drivers, or OL 8 system components that have not been digitally signed using a certificate that is recognized and approved by the organization. prevents CWE-346
  • V-248575 OL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-346
  • V-248827 OL 8 must not have the rsh-server package installed. prevents CWE-346

References