CVE-2021-27799 – CVE-2021-27799 is a stack-based buffer overflow... (How to Fix)

Q: What is the severity of CVE-2021-27799?

CVE-2021-27799 has a CVSS score of 7.5 (HIGH). CVE-2021-27799 is a stack-based buffer overflow vulnerability in the Zint Barcode Generator library's EAN barcode processing function. Attackers can exploit this through applications using the Zint C API to potentially execute arbitrary code or crash applications. This affects any software that incorporates the vulnerable Zint library version.

📋 TL;DR

CVE-2021-27799 is a stack-based buffer overflow vulnerability in the Zint Barcode Generator library's EAN barcode processing function. Attackers can exploit this through applications using the Zint C API to potentially execute arbitrary code or crash applications. This affects any software that incorporates the vulnerable Zint library version.

💻 Affected Systems

Products:

Zint Barcode Generator

Versions: 2.9.1 and earlier

Operating Systems: All platforms where Zint is compiled/used

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects applications using the Zint C API with EAN barcode generation functionality.

📦 What is this software?

Barcode Generator by Zint

View all CVEs affecting Barcode Generator →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution leading to complete system compromise if exploited in internet-facing applications using Zint.

🟠

Likely Case

Application crashes (denial of service) or limited code execution within the application context.

🟢

If Mitigated

No impact if patched version is used or vulnerable functionality is disabled.

🌐 Internet-Facing: MEDIUM - Requires specific application integration and EAN barcode processing.

🏢 Internal Only: LOW - Typically requires user interaction or specific application workflows.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires application integration and specific API calls. Proof of concept exists in the source code repository.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 2.10.0 and later

Vendor Advisory: https://sourceforge.net/p/zint/tickets/218/

Restart Required: Yes

Instructions:

1. Download Zint 2.10.0 or later from sourceforge.net/p/zint. 2. Recompile and replace the vulnerable library. 3. Restart any applications using Zint.

🔧 Temporary Workarounds

Disable EAN barcode processing

all

Modify applications to avoid using the ean_leading_zeroes function in the Zint C API.

🧯 If You Can't Patch

Implement input validation and sanitization for EAN barcode data in applications using Zint.
Use application-level sandboxing or containerization to limit potential impact.

🔍 How to Verify

Check if Vulnerable:

Check if Zint library version is 2.9.1 or earlier in applications using it.

Check Version:

zint --version (if CLI installed) or check library headers in applications

Verify Fix Applied:

Verify Zint library version is 2.10.0 or later and test EAN barcode generation functionality.

📡 Detection & Monitoring

Log Indicators:

Application crashes with Zint library errors
Memory access violation logs

Network Indicators:

Unusual barcode generation requests if network-exposed

SIEM Query:

Process:zint AND (EventID:1000 OR ExceptionCode:c0000005)

📊 Metadata

CVE ID: CVE-2021-27799

CVSS v3 Score: 7.5 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE: CWE-787

Published: February 26, 2021

Last Updated: November 21, 2024

🔗 References

http://zint.org.uk/Manual.aspx?type=p&page=3 Vendor Advisory
http://zint.org.uk/Manual.aspx?type=p&page=4 Vendor Advisory
http://zint.org.uk/Manual.aspx?type=p&page=5 Vendor Advisory
https://sourceforge.net/p/zint/code/ci/7f8c8114f31c09a986597e0ba63a49f96150368a/ Patch,Third Party Advisory
https://sourceforge.net/p/zint/tickets/218/ Exploit,Third Party Advisory
http://zint.org.uk/Manual.aspx?type=p&page=3 Vendor Advisory
http://zint.org.uk/Manual.aspx?type=p&page=4 Vendor Advisory
http://zint.org.uk/Manual.aspx?type=p&page=5 Vendor Advisory
https://sourceforge.net/p/zint/code/ci/7f8c8114f31c09a986597e0ba63a49f96150368a/ Patch,Third Party Advisory
https://sourceforge.net/p/zint/tickets/218/ Exploit,Third Party Advisory

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🔗 Related Vulnerabilities

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