CVE-2025-65026Public exploitNetwork attack vector

Code injection via unescaped CSS template expressions

Published Nov 19, 2025 · Updated Nov 20, 2025

Code injection in esm.sh before 136 allows remote attackers to execute JavaScript by importing crafted CSS as a module. The CSS module branch in server/router.go inserts CSS without backticks directly into a JavaScript template literal and fails to escape ${...} expressions. Execution requires a victim application to import the generated module; browser contexts expose XSS, while Electron contexts expose code execution.

CVSS severity6.1
Medium
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in esm.sh before 136 allows remote attackers to execute JavaScript by importing crafted CSS as a module. The CSS module branch in server/router.go inserts CSS without backticks directly into a JavaScript template literal and fails to escape ${...} expressions. Execution requires a victim application to import the generated module; browser contexts expose XSS, while Electron contexts expose code execution.

The record

CVE
CVE-2025-65026
Published
Nov 19, 2025
Updated
Nov 20, 2025
Vendor
esm-dev
Product
esm.sh
Classifications
CWE-94, CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 19, 2025CVE publishedPublication date reported by the CVE source.
  2. Nov 20, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 136

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

esm-dev · esm.shversion=< 136

Published CVSS scores

6.1GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
9.6NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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