CVE-2026-31943CWE-918

LibreChat has SSRF protection bypass via IPv4-mapped IPv6 normalization in isPrivateIP

High · published March 27, 2026

CVSS v3.1
8.5
EPSS
0%
Percentile
21.7
In the wild
Unconfirmed
What it is

LibreChat is a ChatGPT clone with additional features. Prior to version 0.8.3, `isPrivateIP()` in `packages/api/src/auth/domain.ts` fails to detect IPv4-mapped IPv6 addresses in their hex-normalized form, allowing any authenticated user to bypass SSRF protection and make the server issue HTTP requests to internal network resources — including cloud metadata services (e.g., AWS `169.254.169.254`), loopback, and RFC1918 ranges. Version 0.8.3 fixes the issue.

The record
Technical detail
CVSS v3.1
8.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00302 · 21.7th percentile
Weakness
CWE-918 · Server-Side Request Forgery (SSRF)
Published
2026-03-27T19:21Z
EPSS history
Timeline
  • 27 MAR 19:21Z
    LibreChat has SSRF protection bypass via IPv4-mapped IPv6 normalization in isPrivateIP
    cvelistv5