CVE-2021-3580
📋 TL;DR
CVE-2021-3580 is a vulnerability in nettle's RSA decryption functions where specially crafted ciphertext can cause application crashes and denial of service. This affects systems using nettle cryptographic library for RSA operations. Applications that process untrusted RSA ciphertext are vulnerable.
💻 Affected Systems
- nettle cryptographic library
- Applications using nettle for RSA operations
📦 What is this software?
Nettle by Nettle Project
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service for applications using nettle RSA decryption, potentially affecting critical services that rely on RSA operations for security.
Likely Case
Application crashes leading to service disruption when processing malicious RSA ciphertext, requiring restart of affected services.
If Mitigated
Minimal impact if systems are patched or don't process untrusted RSA ciphertext; isolated service restarts may be needed.
🎯 Exploit Status
Exploitation requires sending specially crafted RSA ciphertext to vulnerable applications; no authentication needed if application accepts external RSA-encrypted data.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: nettle 3.7.3 and later
Vendor Advisory: https://bugzilla.redhat.com/show_bug.cgi?id=1967983
Restart Required: Yes
Instructions:
1. Update nettle package to version 3.7.3 or later using your distribution's package manager. 2. Restart all applications using nettle library. 3. For Red Hat systems: 'yum update nettle'. For Debian/Ubuntu: 'apt update && apt upgrade nettle'. For Gentoo: emerge --sync && emerge -av nettle'.
🔧 Temporary Workarounds
Input validation for RSA ciphertext
allImplement strict validation of RSA ciphertext before passing to nettle decryption functions
Rate limiting RSA decryption operations
allLimit the rate of RSA decryption operations to mitigate DoS impact
🧯 If You Can't Patch
- Implement network filtering to block or limit RSA-encrypted traffic from untrusted sources
- Deploy application-level monitoring and automatic restart mechanisms for services using nettle RSA decryption
🔍 How to Verify
Check if Vulnerable:
Check nettle version: 'nettle-hash --version' or 'dpkg -l | grep nettle' or 'rpm -q nettle'. If version is below 3.7.3, system is vulnerable.Check Version:
nettle-hash --version 2>/dev/null || dpkg -l | grep nettle 2>/dev/null || rpm -q nettle 2>/dev/null || echo 'nettle not found'Verify Fix Applied:
Verify nettle version is 3.7.3 or later using same commands, then test RSA decryption functionality in applications.📡 Detection & Monitoring
Log Indicators:
- Application crashes or segmentation faults in processes using nettle RSA functions
- High frequency of RSA decryption failures
Network Indicators:
- Unusual patterns of RSA-encrypted traffic to vulnerable services
- Multiple connection attempts with malformed cryptographic data
SIEM Query:
source="application.logs" AND ("segmentation fault" OR "SIGSEGV") AND process="*nettle*" OR "RSA decrypt"🔗 References
- https://bugzilla.redhat.com/show_bug.cgi?id=1967983
- https://lists.debian.org/debian-lts-announce/2021/09/msg00008.html
- https://security.gentoo.org/glsa/202401-24
- https://security.netapp.com/advisory/ntap-20211104-0006/
- https://bugzilla.redhat.com/show_bug.cgi?id=1967983
- https://lists.debian.org/debian-lts-announce/2021/09/msg00008.html
- https://security.gentoo.org/glsa/202401-24
- https://security.netapp.com/advisory/ntap-20211104-0006/
