EspoCRM Time-of-check Time-of-use (TOCTOU) Race Condition Vulnerability - CVE-2026-33659 - Vulnerability Database

EspoCRM Time-of-check Time-of-use (TOCTOU) Race Condition Vulnerability - CVE-2026-33659

Low

Reference: CVE-2026-33659

NVD Link: https://nvd.nist.gov/vuln/detail/CVE-2026-33659

Title: EspoCRM Time-of-check Time-of-use (TOCTOU) Race Condition Vulnerability

Overview:

EspoCRM is an open source customer relationship management application. In versions 9.3.3 and below the POST /api/v1/Attachment/fromImageUrl endpoint is vulnerable to Server-Side Request Forgery (SSRF) via a DNS rebinding (TOCTOU) condition. Host validation uses dns_get_record() but the actual HTTP request resolves hostnames through curl39s internal resolver (gethostbyname()) allowing the two lookups to return different IP addresses for the same hostname. A secondary issue exists where an empty DNS result (due to DNS failure IPv6-only domains or non-existent hostnames) causes the validation to implicitly allow the host without further checks. An authenticated attacker with default attachment creation access can exploit this gap to bypass internal IP restrictions and scan internal network ports confirm the existence of internal hosts and interact with internal HTTP-based services though data extraction from binary protocol services and remote code execution are not possible through this endpoint. This issue has been fixed in version 9.3.4.