CVE-2025-66452Public exploitNetwork attack vector

Reflected XSS via malformed JSON error response

Published Dec 11, 2025 · Updated Dec 11, 2025

Reflected XSS in LibreChat 0.8.1 and earlier allows remote attackers to inject script through malformed JSON API requests. Express JSON parsing errors embed the entire untrusted request body in a SyntaxError response without sanitization or a dedicated error handler. Execution requires a browser to render that response as HTML; the published reproduction uses an authenticated prompt request and shows script-capable content reflected unchanged.

CVSS severity5.3
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in LibreChat 0.8.1 and earlier allows remote attackers to inject script through malformed JSON API requests. Express JSON parsing errors embed the entire untrusted request body in a SyntaxError response without sanitization or a dedicated error handler. Execution requires a browser to render that response as HTML; the published reproduction uses an authenticated prompt request and shows script-capable content reflected unchanged.

The record

CVE
CVE-2025-66452
Published
Dec 11, 2025
Updated
Dec 11, 2025
Vendor
Danny Avila
Product
LibreChat
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 11, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 11, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=<= 0.8.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Danny Avila · LibreChatversion=<= 0.8.1

Published CVSS scores

5.3GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

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.

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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-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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