CVE-2018-20311

Local privilege escalation via proxyCPDFAction stack overflow

Published Jan 7, 2021 · Updated Aug 5, 2024

Stack overflow in Foxit Reader before 9.5 and PhantomPDF before 8.3.10 or 9.x before 9.5 allows local users to run code at medium integrity. The proxyCPDFAction request handler fails to validate a user-supplied large integer or long string, allowing concurrent processing to overrun a stack buffer or read beyond its bounds. Exploitation requires the ability to run low-privileged code locally, and successful exploitation elevates execution to medium integrity.

CVSS severity8.1
High
EPSS probability0.82%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack overflow in Foxit Reader before 9.5 and PhantomPDF before 8.3.10 or 9.x before 9.5 allows local users to run code at medium integrity. The proxyCPDFAction request handler fails to validate a user-supplied large integer or long string, allowing concurrent processing to overrun a stack buffer or read beyond its bounds. Exploitation requires the ability to run low-privileged code locally, and successful exploitation elevates execution to medium integrity.

The record

CVE
CVE-2018-20311
Published
Jan 7, 2021
Updated
Aug 5, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, CWE-362, CWE-125, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
8.1NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
CWE-125Out-of-bounds Read
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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