CVE-2026-31431 Overview
A vulnerability has been identified in the Linux kernel's cryptographic subsystem, specifically within the algif_aead module. The issue stems from complexity introduced by in-place operation handling in the AEAD (Authenticated Encryption with Associated Data) socket interface. This vulnerability required a revert of commit 72548b093ee3 to resolve issues related to memory handling when the source and destination data originate from different memory mappings.
Critical Impact
The vulnerability affects the kernel's cryptographic interface, potentially impacting systems utilizing the AF_ALG socket interface for AEAD operations. Improper handling of in-place operations could lead to memory corruption or unexpected behavior.
Affected Products
- Linux Kernel (versions with commit 72548b093ee3 applied)
- Systems utilizing the AF_ALG socket interface for AEAD cryptographic operations
- Linux distributions running affected kernel versions
Discovery Timeline
- 2026-04-22 - CVE-2026-31431 published to NVD
- 2026-04-23 - Last updated in NVD database
Technical Details for CVE-2026-31431
Vulnerability Analysis
The vulnerability exists within the algif_aead module of the Linux kernel's cryptographic subsystem. The AF_ALG interface provides userspace applications with access to kernel cryptographic functionality, and AEAD is a cryptographic mode that provides both confidentiality and authenticity guarantees.
The problematic code attempted to perform in-place cryptographic operations where the source and destination buffers could theoretically overlap. However, in the context of algif_aead, source and destination data originate from different memory mappings, making in-place operation both unnecessary and potentially dangerous. The complexity added to support in-place operations introduced handling issues that could affect the integrity of cryptographic operations.
Root Cause
The root cause lies in commit 72548b093ee3, which added complexity for in-place operation support in the AEAD socket interface. Since source and destination data in algif_aead come from different memory mappings, there was no practical benefit to operating in-place. The added complexity for handling associated data (AD) copying in this context introduced potential memory handling issues that needed to be resolved.
Attack Vector
The attack vector for this vulnerability involves interaction with the AF_ALG socket interface. An attacker with local access could potentially leverage improper memory handling during AEAD cryptographic operations. The vulnerability requires the ability to create AF_ALG sockets and perform AEAD encryption/decryption operations.
The fix reverts to out-of-place operation, directly copying the associated data without the problematic in-place handling logic. This simplifies the code path and eliminates the potential for memory mishandling between different memory mappings.
Detection Methods for CVE-2026-31431
Indicators of Compromise
- Unexpected kernel crashes or panics related to the crypto subsystem
- Anomalous behavior in applications using the AF_ALG socket interface for AEAD operations
- Kernel log entries indicating issues with algif_aead or cryptographic socket operations
Detection Strategies
- Monitor kernel logs for crypto subsystem errors, particularly those referencing algif_aead or AEAD socket operations
- Deploy kernel runtime integrity monitoring to detect exploitation attempts targeting the cryptographic subsystem
- Utilize SentinelOne Singularity platform for real-time kernel-level threat detection and behavioral analysis
Monitoring Recommendations
- Enable kernel audit logging for AF_ALG socket operations
- Configure alerting for unusual cryptographic API usage patterns
- Monitor for processes unexpectedly accessing the kernel cryptographic interface
How to Mitigate CVE-2026-31431
Immediate Actions Required
- Review current kernel version to determine if the vulnerable commit 72548b093ee3 is present
- Apply kernel patches from the provided kernel git commits as soon as possible
- Consider restricting access to the AF_ALG socket interface if not required for operations
Patch Information
Patches are available through the Linux kernel stable tree. The fix reverts the problematic in-place operation handling and simplifies AD copying in the algif_aead module. Multiple patch commits are available:
Workarounds
- Restrict access to the AF_ALG socket interface using kernel configuration or security modules if immediate patching is not feasible
- Apply SELinux or AppArmor policies to limit which processes can access the cryptographic socket interface
- Consider disabling the algif_aead module if AEAD socket operations are not required in your environment
# Check if algif_aead module is loaded
lsmod | grep algif_aead
# Optionally blacklist the module if not required (temporary workaround)
echo "blacklist algif_aead" >> /etc/modprobe.d/blacklist-algif-aead.conf
# Unload the module if currently loaded
modprobe -r algif_aead
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
