CVE-2026-31943Public exploitNetwork attack vector

Authenticated SSRF via IPv4-mapped IPv6 normalization

Published Mar 27, 2026 · Updated Mar 27, 2026

Server-side request forgery in LibreChat before 0.8.3 allows remote authenticated users to access internal resources through agent actions. The isPrivateIP function checks IPv4-mapped IPv6 addresses only in dotted-decimal form after Node.js URL parsing has normalized them to hexadecimal, so the private-address test misses them. An account with access to agent actions can make the server request loopback, RFC1918, or cloud metadata endpoints and read data returned by those services.

CVSS severity8.5
High
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Server-side request forgery in LibreChat before 0.8.3 allows remote authenticated users to access internal resources through agent actions. The isPrivateIP function checks IPv4-mapped IPv6 addresses only in dotted-decimal form after Node.js URL parsing has normalized them to hexadecimal, so the private-address test misses them. An account with access to agent actions can make the server request loopback, RFC1918, or cloud metadata endpoints and read data returned by those services.

The record

CVE
CVE-2026-31943
Published
Mar 27, 2026
Updated
Mar 27, 2026
Vendor
Danny Avila
Product
LibreChat
Classifications
CWE-918, T1552.005
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 27, 2026Record 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=< 0.8.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Danny Avila · LibreChatversion=< 0.8.3

Published CVSS scores

8.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
T1552.005Unsecured Credentials: Cloud Instance Metadata API

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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