CVE-2026-31945 is a server-side request forgery (SSRF) vulnerability in the danny-avila LibreChat product, specifically affecting versions from 0.8.2-rc2 up to but not including 0.8.3-rc1. The vulnerability occurs when using agent actions or MCP features. Although a prior SSRF vulnerability was patched by adding hostname validation, this fix did not verify whether the DNS resolution pointed to private IP addresses. Consequently, attackers can exploit this to access internal resources such as internal RAG APIs or cloud instance metadata endpoints. The vulnerability has a CVSS 3.1 score of 7.7 (high severity) with network attack vector, low attack complexity, requiring low privileges and no user interaction, and impacts confidentiality with scope change. The issue is fixed in version 0.8.3-rc1.

Successful exploitation allows an attacker to perform SSRF attacks that can access internal network resources and sensitive endpoints such as cloud instance metadata services. This can lead to unauthorized disclosure of sensitive information within the internal network environment. The vulnerability does not affect integrity or availability directly but has a high confidentiality impact and changes the security scope.

Upgrade affected LibreChat instances to version 0.8.3-rc1 or later, which contains the patch addressing this SSRF vulnerability by properly validating DNS resolution results to prevent access to private IP addresses. No other mitigations are indicated by the vendor advisory.