CVE-2026-31943 | LibreChat has SSRF protection bypass via IPv4-mapped IPv6 normalization in isPrivateIP

Exp

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.

Published: 2026-03-27 Last update: 2026-03-31 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-31943 is rated Exploit Available (51.8/100): CVSS High severity, with low exploitation likelihood (EPSS 0.03%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-31943

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-31943

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-28 — 0.03% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-31943

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 3.1 4.7 [email protected]

Weakness enumeration for CVE-2026-31943

Affected software / configurations for CVE-2026-31943

Vendor Product Version Raw CPE
librechat librechat < 0.8.3 cpe:2.3:a:librechat:librechat:*:*:*:*:*:*:*:*
librechat librechat 0.8.3 cpe:2.3:a:librechat:librechat:0.8.3:rc1:*:*:*:*:*:*
librechat librechat 0.8.3 cpe:2.3:a:librechat:librechat:0.8.3:rc2:*:*:*:*:*:*

References for CVE-2026-31943

cvelogic Threat Intelligence