CVE-2021-31239 – CVE-2021-31239 is an out-of-bounds read vulnera... (How to Fix)

Q: What is the severity of CVE-2021-31239?

CVE-2021-31239 has a CVSS score of 7.5 (HIGH). CVE-2021-31239 is an out-of-bounds read vulnerability in SQLite's appendvfs.c that allows remote attackers to cause denial of service through application crashes. This affects applications using SQLite 3.35.4 and earlier versions. The vulnerability can be triggered when specially crafted database operations are processed.

📋 TL;DR

CVE-2021-31239 is an out-of-bounds read vulnerability in SQLite's appendvfs.c that allows remote attackers to cause denial of service through application crashes. This affects applications using SQLite 3.35.4 and earlier versions. The vulnerability can be triggered when specially crafted database operations are processed.

💻 Affected Systems

Products:

SQLite
Applications embedding SQLite library
Database systems using SQLite

Versions: SQLite 3.35.4 and earlier versions

Operating Systems: All operating systems running vulnerable SQLite versions

Default Config Vulnerable: ⚠️ Yes

Notes: Any application or system using the vulnerable SQLite version is affected regardless of configuration.

📦 What is this software?

Sqlite by Sqlite

View all CVEs affecting Sqlite →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete application/service crash leading to sustained denial of service, potentially allowing attackers to disrupt critical database operations.

🟠

Likely Case

Application instability and intermittent crashes affecting database availability and reliability.

🟢

If Mitigated

Minimal impact with proper input validation and database isolation in place.

🌐 Internet-Facing: MEDIUM - Requires specific database operations to trigger, but can be exploited remotely if application exposes database functionality.

🏢 Internal Only: MEDIUM - Internal applications using vulnerable SQLite versions remain susceptible to exploitation.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires ability to execute specific database operations against vulnerable SQLite instances.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: SQLite 3.35.5 and later

Vendor Advisory: https://sqlite.org/releaselog/3_35_5.html

Restart Required: Yes

Instructions:

1. Update SQLite to version 3.35.5 or later. 2. For embedded applications, update the SQLite library. 3. Restart affected applications/services. 4. For Linux distributions, use package manager: 'sudo apt update && sudo apt upgrade sqlite3' or equivalent.

🔧 Temporary Workarounds

Input Validation

all

Implement strict input validation for database operations to prevent malicious queries.

Database Isolation

all

Run SQLite databases in isolated environments with limited privileges.

🧯 If You Can't Patch

Implement network segmentation to limit access to SQLite services
Deploy application-level firewalls to filter suspicious database operations

🔍 How to Verify

Check if Vulnerable:

Check SQLite version: 'sqlite3 --version' or examine application dependencies for SQLite library version.

Check Version:

sqlite3 --version

Verify Fix Applied:

Confirm SQLite version is 3.35.5 or later and test database operations that previously caused issues.

📡 Detection & Monitoring

Log Indicators:

Application crashes with segmentation faults
Database connection failures
Unusual database operation patterns

Network Indicators:

Repeated connection attempts to database ports
Unusual query patterns to SQLite services

SIEM Query:

source="application.logs" AND ("segmentation fault" OR "sqlite" AND "crash")

📊 Metadata

CVE ID: CVE-2021-31239

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-125

Published: May 9, 2023

Last Updated: May 5, 2025

🔗 References

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