CVE-2026-21507: iccDEV CalcProfileID DoS Vulnerability

CVE-2026-21507 Overview

CVE-2026-21507 is an Infinite Loop vulnerability affecting iccDEV, a widely-used set of libraries and tools for working with ICC (International Color Consortium) color management profiles. The vulnerability exists in the CalcProfileID function within IccProfile.cpp, where improper loop termination conditions can cause the application to enter an infinite loop, leading to denial of service conditions.

Critical Impact

Applications processing malformed ICC profiles may hang indefinitely, causing resource exhaustion and denial of service. Systems relying on iccDEV for color management operations are at risk of becoming unresponsive.

Affected Products

• iccDEV versions 2.3.1 and below
• Applications integrating iccDEV color management libraries
• Systems processing ICC color profiles using vulnerable iccDEV versions

Discovery Timeline

• 2026-01-06 - CVE CVE-2026-21507 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2026-21507

Vulnerability Analysis

This vulnerability is classified as CWE-835 (Loop with Unreachable Exit Condition), commonly known as an infinite loop vulnerability. The flaw resides in the CalcProfileID function in IccProfLib/IccProfile.cpp, which is responsible for calculating the MD5-based Profile ID for ICC color profiles.

The vulnerable code contains a while loop that processes profile data in 1024-byte blocks. The loop relies on the Read8 function to read data from an I/O stream and decrements a length counter accordingly. However, when the Read8 function returns zero bytes (indicating no more data can be read), the loop fails to detect this condition and continues iterating indefinitely. Since len is never decremented when num is zero, the exit condition while(len) is never satisfied, causing the application to hang.

This vulnerability can be triggered by supplying a malformed or truncated ICC profile that causes the I/O read operation to fail prematurely, resulting in continuous zero-byte reads while the length counter remains positive.

Root Cause

The root cause is the absence of a guard condition to handle cases where the I/O read operation returns zero bytes. The original implementation assumed that Read8 would always return the expected number of bytes until the entire profile was read, without accounting for error conditions or unexpected end-of-stream scenarios. This oversight allows the loop to continue indefinitely when the I/O stream is exhausted prematurely while len still holds a positive value.

Attack Vector

An attacker can exploit this vulnerability by crafting a malicious ICC color profile with inconsistent header length values or by providing a truncated profile file. When an application using the vulnerable iccDEV library attempts to calculate the Profile ID for such a file, the CalcProfileID function enters an infinite loop. This attack can be delivered through any vector that causes the application to process ICC profiles, including:

• Uploaded image files containing embedded ICC profiles
• Document processing pipelines handling color-managed content
• Print spooling systems processing color profiles
• Web applications that perform server-side color conversion

   nBlock = 0;
   while(len) {
     size_t num = pIO->Read8(&buffer[0],1024);
+    if (num == 0)
+        break;              // can't give a useful error here, but we need to break the infinite loop
     if (!nBlock) {  // Zero out 3 header contents in Profile ID calculation
       memset(buffer+44, 0, 4); //Profile flags
       memset(buffer+64, 0, 4);  //Rendering Intent
       memset(buffer+84, 0, 16); //Profile Id
     }
     icMD5Update(&context,buffer, (unsigned int) num);
     nBlock++;
-    len -=num;
+    len -= num;
   }
   icMD5Final(&pProfileID->ID8[0],&context);

Source: GitHub Commit Details

Detection Methods for CVE-2026-21507

Indicators of Compromise

• Application processes consuming 100% CPU indefinitely while processing ICC profiles
• Hung or unresponsive services that handle color profile operations
• Memory and resource exhaustion on systems processing user-supplied image files
• Thread pools depleted by blocked workers stuck in CalcProfileID function calls

Detection Strategies

• Monitor for process CPU utilization spikes correlated with ICC profile processing activities
• Implement application-level timeouts for color profile parsing operations
• Use static analysis tools to identify iccDEV library versions below 2.3.1.1 in your codebase
• Deploy runtime application self-protection (RASP) to detect infinite loop conditions

Monitoring Recommendations

• Configure process monitoring to alert on sustained high CPU usage from applications using iccDEV
• Implement watchdog timers for services that process color management profiles
• Log and monitor ICC profile processing events to identify potential exploitation attempts
• Audit dependency manifests to track vulnerable iccDEV library versions across your environment

How to Mitigate CVE-2026-21507

Immediate Actions Required

• Upgrade iccDEV to version 2.3.1.1 or later immediately
• Audit all applications and services that depend on iccDEV for color management functionality
• Implement input validation and size limits for ICC profile processing
• Consider deploying application-level timeouts as defense-in-depth

Patch Information

The vulnerability has been fixed in iccDEV version 2.3.1.1. The patch adds a check for zero-byte reads in the CalcProfileID function, breaking out of the loop when no more data can be read from the I/O stream. Users should update to the patched version by pulling the latest release from the International Color Consortium GitHub repository. Technical details of the fix are available in the GitHub commit and GitHub Security Advisory GHSA-hgp5-r8m9-8qpj.

Workarounds

• Implement timeouts around ICC profile processing operations to prevent indefinite hangs
• Validate ICC profile header length values against actual file sizes before processing
• Restrict processing of ICC profiles to trusted sources only until patching is complete
• Run ICC profile processing in isolated sandboxed environments with resource limits

# Configuration example - setting process resource limits
# Limit CPU time for profile processing to prevent infinite loops from exhausting resources
ulimit -t 60  # Set 60-second CPU time limit for the current shell session

# Alternatively, use systemd resource controls for services
# Add to your service unit file:
# [Service]
# CPUQuota=50%
# TimeoutStartSec=30