CVE-2026-48373: Acrobat Reader Buffer Overflow Vulnerability

CVE-2026-48373 Overview

CVE-2026-48373 is a heap-based buffer overflow vulnerability [CWE-122] affecting Adobe Acrobat Reader. Successful exploitation allows an attacker to execute arbitrary code in the context of the current user. The flaw requires user interaction, meaning a victim must open a specially crafted malicious file for exploitation to succeed. Adobe addressed the issue in security bulletin APSB26-63.

Critical Impact
Arbitrary code execution in the context of the current user through a maliciously crafted document opened in Adobe Acrobat Reader.

Affected Products

Adobe Acrobat Reader (see APSB26-63 for affected versions)
Adobe Acrobat (see APSB26-63 for affected versions)

Discovery Timeline

2026-07-17 - CVE-2026-48373 published to the National Vulnerability Database (NVD)
2026-07-23 - Last updated in NVD database

Technical Details for CVE-2026-48373

Vulnerability Analysis

The vulnerability is a heap-based buffer overflow [CWE-122] within Adobe Acrobat Reader's file parsing logic. When Reader processes a malformed document, memory allocated on the heap is written beyond its intended bounds. This corruption can overwrite adjacent heap metadata or object pointers used by the application. An attacker who controls the overflowing data can steer program execution toward attacker-supplied code.

Because the attack vector is local and requires user interaction, exploitation typically occurs through phishing campaigns delivering weaponized PDF files. Code executes with the privileges of the user opening the document. On systems where users hold administrative rights, the impact extends to full host compromise.

Root Cause

The root cause is improper validation of size or length parameters used when allocating or copying data onto a heap buffer during document parsing. When the parser encounters crafted structures whose declared sizes differ from actual data lengths, it writes past the allocated region. Details about the specific parsing routine are documented in the Adobe Security Patch APSB26-63.

Attack Vector

An attacker crafts a malicious PDF containing structures that trigger the heap overflow during rendering. The file is delivered through email attachments, drive-by download, or messaging platforms. When the victim opens the document in a vulnerable version of Acrobat Reader, the overflow occurs and attacker-controlled data can hijack execution flow. The Exploit Prediction Scoring System (EPSS) reports a probability of 0.186% at the 8.471 percentile as of 2026-07-24.

Detection Methods for CVE-2026-48373

Indicators of Compromise

Unexpected child processes spawned from AcroRd32.exe or Acrobat.exe, particularly command interpreters such as cmd.exe, powershell.exe, or wscript.exe
PDF files arriving through email with obfuscated JavaScript, embedded streams, or unusually large object structures
Acrobat Reader processes making outbound network connections to unfamiliar hosts shortly after document open events
Crashes or exception events logged for Acrobat Reader coinciding with document opening

Detection Strategies

Deploy behavioral endpoint monitoring to flag process lineage anomalies where Acrobat spawns scripting engines or shells
Inspect email gateways for PDFs containing embedded JavaScript, launch actions, or malformed cross-reference tables
Correlate endpoint telemetry with user document open events to identify exploitation attempts against unpatched hosts

Monitoring Recommendations

Enable Microsoft Defender Attack Surface Reduction rules that block child process creation from Office and PDF readers
Log and alert on writes to autorun locations and scheduled task creation following Acrobat process activity
Track Acrobat Reader version inventory across the fleet to identify hosts running unpatched builds

How to Mitigate CVE-2026-48373

Immediate Actions Required

Apply the Adobe security updates referenced in APSB26-63 to all Acrobat and Acrobat Reader installations
Restrict local administrator rights on user workstations to limit the impact of user-context code execution
Block inbound PDF attachments from untrusted external senders at the email gateway pending patch deployment

Patch Information

Adobe published the fix in security bulletin APSB26-63. Administrators should identify affected product versions listed in the advisory and update to the fixed release. Enterprise deployments managed through SCCM, Intune, or Adobe Admin Console should push the update to all endpoints as a priority.

Workarounds

Enable Protected View in Acrobat Reader to sandbox documents originating from the internet or email attachments
Disable JavaScript execution within Acrobat Reader via Preferences > JavaScript > Enable Acrobat JavaScript
Configure Group Policy to route untrusted PDF opens through an isolated browser or sandboxed viewer

bash

# Configuration example: disable Acrobat JavaScript via registry (Windows)
reg add "HKCU\Software\Adobe\Acrobat Reader\DC\JSPrefs" /v bEnableJS /t REG_DWORD /d 0 /f

# Enforce Protected View for all files
reg add "HKCU\Software\Adobe\Acrobat Reader\DC\TrustManager" /v iProtectedView /t REG_DWORD /d 2 /f