Cyber Posture

CVE-2025-56218

Critical

Published: 17 October 2025

Published
17 October 2025
Modified
27 October 2025
KEV Added
—
Patch
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CVSS Score 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0015 34.7th percentile
Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Description

Adversaries may send spearphishing messages via third-party services in an attempt to gain access to victim systems.

Security Summary

CVE-2025-56218 is an arbitrary file upload vulnerability in SigningHub version 8.6.8 that enables attackers to execute arbitrary code by uploading a crafted PDF file. This issue, published on 2025-10-17, is classified under CWE-434 (Unrestricted Upload of File with Dangerous Type) and carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), marking it as critical due to its high impact on confidentiality, integrity, and availability.

Unauthenticated remote attackers can exploit this vulnerability over the network with low attack complexity and no user interaction required. By uploading a specially crafted PDF file, attackers achieve arbitrary code execution on the targeted SigningHub instance, potentially leading to full system compromise.

Mitigation guidance and further details are available in vendor advisories from Ascertia (http://ascertia.com), SigningHub (http://signinghub.com), and the GitHub repository documenting the vulnerability (https://github.com/saykino/CVE-2025-56218).

Details

CWE(s)
CWE-434

Affected Products

ascertia
signinghub
≤ 8.6.8

MITRE ATT&CK Enterprise Techniques

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1566.001 Spearphishing Attachment Initial Access
Adversaries may send spearphishing emails with a malicious attachment in an attempt to gain access to victim systems.
attack.mitre.org →
T1566.002 Spearphishing Link Initial Access
Adversaries may send spearphishing emails with a malicious link in an attempt to gain access to victim systems.
attack.mitre.org →
T1566.003 Spearphishing via Service Initial Access
Adversaries may send spearphishing messages via third-party services in an attempt to gain access to victim systems.
attack.mitre.org →
Why these techniques?

Arbitrary file upload vulnerability in web-based SigningHub enables exploitation of a public-facing application (T1190) and facilitates spearphishing via service (T1566.003) by uploading crafted files (Excel/PDF with scripts or disguised phishing URLs) that are converted and delivered to recipients, leading to malicious file (T1566.001) or link (T1566.002) execution upon interaction.

References