CVE-2018-18688

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-01-07 · updated 2026-06-17
Weakness: CWE-347

Description

The Portable Document Format (PDF) specification does not provide any information regarding the concrete procedure of how to validate signatures. Consequently, an Incremental Saving vulnerability exists in multiple products. When an attacker uses the Incremental Saving feature to add pages or annotations, Body Updates are displayed to the user without any action by the signature-validation logic. This affects Foxit Reader before 9.4 and PhantomPDF before 8.3.9 and 9.x before 9.4. It also affects LibreOffice, Master PDF Editor, Nitro Pro, Nitro Reader, Nuance Power PDF Standard, PDF Editor 6 Pro, PDFelement6 Pro, PDF Studio Viewer 2018, PDF Studio Pro, Perfect PDF 10 Premium, and Perfect PDF Reader.

Affected products

Code-Industry Master Pdf Editor: 5.1.12, 5.1.68, 5.1.24
Foxit Reader: 9.4, 9.1.0, 9.2.0
Foxit PhantomPDF: from 9.0 before 9.4; 8.3.9 — fixed in 9.4
Nitro Pro: 11.0.3.173
Gonitro Nitro Reader: 5.5.9.2
Iskysoft Pdf Editor 6: 6.4.2.3521, 6.6.2.3315, 6.7.6.3399
Iskysoft Pdfelement6: 6.8.0.3523, 6.8.4.3921, 6.7.1.3355, 6.7.6.3399
The Document Foundation LibreOffice: 6.0.6.2, 6.1.3.2, 6.1.0.3
Nuance Power Pdf Standard: 3.0.0.17, 3.0.0.30, 7.0
Qoppa Pdf Studio: 12.0.7
Qoppa Pdf Studio Viewer 2018: 2018.0.1, 2018.2.0
Soft-Xpansion Perfect Pdf 10: 10.0.0.1
Soft-Xpansion Perfect Pdf Reader: 13.0.3, 13.1.5

How to fix

Upgrade to a fixed version: Foxit PhantomPDF 9.4. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2018-18688 or the next vulnerability affects your stack