CVE-2024-47076: Libcupsfilters Info Disclosure Flaw

CVE-2024-47076 Overview

CUPS is a standards-based, open-source printing system, and libcupsfilters contains the code of the filters of the former cups-filters package as library functions to be used for the data format conversion tasks needed in Printer Applications. The cfGetPrinterAttributes5 function in libcupsfilters does not sanitize IPP attributes returned from an IPP server. When these IPP attributes are used, for instance, to generate a PPD file, this can lead to attacker controlled data to be provided to the rest of the CUPS system.

Critical Impact

Improper input sanitization in cfGetPrinterAttributes5 can be exploited remotely, leading to potential data manipulation within CUPS.

Affected Products

• openprinting libcupsfilters

Discovery Timeline

• Not Available - Vulnerability discovered by Not Available
• Not Available - Responsible disclosure to openprinting
• Not Available - CVE CVE-2024-47076 assigned
• Not Available - openprinting releases security patch
• 2024-09-26 - CVE CVE-2024-47076 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2024-47076

Vulnerability Analysis

The vulnerability stems from improper input validation within the cfGetPrinterAttributes5 function. This leads to unsanitized IPP attributes being processed, potentially allowing an attacker to inject malicious data that influences the CUPS printing process.

Root Cause

The root cause is the lack of proper input sanitization mechanisms for IPP attributes in the cfGetPrinterAttributes5 function.

Attack Vector

Network-based attacks can exploit this vulnerability by sending crafted IPP responses to a vulnerable service.

// Example exploitation code (sanitized)
char *generateMaliciousPPD(char *ippData) {
    char *ppd = (char *)malloc(1024);
    snprintf(ppd, 1024, "*PPD-Adobe: \"3.0\"\n%s\n", ippData);
    return ppd;
}

Detection Methods for CVE-2024-47076

Indicators of Compromise

• Unusual PPD files being generated
• Unexpected IPP traffic to printers
• Logs showing malformed or abnormal IPP attributes

Detection Strategies

Monitoring for unexpected changes in PPD file creation and analyzing IPP traffic for irregularities can help detect exploitation attempts.

Monitoring Recommendations

Implement network traffic analysis focusing on IPP protocol exchanges and conduct regular audits of generated PPD files.

How to Mitigate CVE-2024-47076

Immediate Actions Required

• Block suspicious IPP traffic at the network level
• Review and secure PPD file generation processes
• Update libcupsfilters to the latest patched version

Patch Information

Patches have been released by openprinting in the commit 95576ec3d20c109332d14672a807353cdc551018.

Workarounds

Until a patch can be applied, consider disabling or restricting network access to the printing service.

# Configuration example
echo "Disabling network access to CUPS"
iptables -A INPUT -p tcp --dport 631 -j DROP