CVE-2026-31632 Overview
CVE-2026-31632 is a memory leak vulnerability in the Linux kernel's rxrpc subsystem. Specifically, the rxgk_verify_response() function fails to properly clean up the rxgk context it creates, leading to memory resource exhaustion over time. This vulnerability affects the RxRPC protocol implementation used for secure network communications, particularly in AFS (Andrew File System) environments.
Critical Impact
Local attackers with low privileges can exploit this memory leak to cause denial of service conditions by exhausting system memory resources through repeated triggering of the vulnerable code path.
Affected Products
- Linux Kernel versions 6.15.x through 6.16
- Linux Kernel 7.0 Release Candidates (rc1 through rc7)
- Linux Kernel systems using rxrpc/rxgk authentication
Discovery Timeline
- 2026-04-24 - CVE-2026-31632 published to NVD
- 2026-04-27 - Last updated in NVD database
Technical Details for CVE-2026-31632
Vulnerability Analysis
This vulnerability is classified as CWE-401 (Missing Release of Memory after Effective Lifetime). The rxgk_verify_response() function in the Linux kernel's rxrpc subsystem creates an rxgk security context during the authentication response verification process. However, under certain error conditions or normal execution paths, this context is not properly freed before the function returns.
The rxgk (RxRPC GSS-API) security mechanism is used to provide authenticated and encrypted communications for services like AFS. When the verification function allocates memory for the context structure but fails to release it, this memory becomes unreachable and cannot be reclaimed by the system.
Root Cause
The root cause is a missing cleanup routine in the rxgk_verify_response() function. When the function creates an rxgk context to verify an incoming authentication response, it allocates kernel memory. If the verification process encounters an error or completes without properly deallocating this context, the memory remains allocated indefinitely. This represents a classic resource leak pattern where memory allocation is not paired with corresponding deallocation in all code paths.
Attack Vector
The vulnerability requires local access to the system with low privileges. An attacker can exploit this by repeatedly triggering the rxgk verification process, causing incremental memory consumption that eventually leads to system instability or denial of service.
The attack does not require user interaction and does not affect the confidentiality or integrity of the system—the impact is limited to availability. A local user or process that can initiate rxrpc connections could systematically trigger the memory leak by forcing authentication verification attempts, gradually depleting available kernel memory.
Detection Methods for CVE-2026-31632
Indicators of Compromise
- Gradual increase in kernel memory usage without corresponding process activity
- System logs showing memory allocation failures or out-of-memory conditions
- Degraded system performance correlating with rxrpc/AFS authentication activity
- Elevated MemFree depletion in /proc/meminfo over extended periods
Detection Strategies
- Monitor kernel slab allocator statistics for growing unreclaimable memory allocations
- Implement memory usage trending alerts for systems running AFS or rxrpc-dependent services
- Use kernel debugging tools like kmemleak to identify memory leaks in the rxgk subsystem
- Review system logs for rxrpc-related error messages or authentication failures
Monitoring Recommendations
- Configure alerting thresholds for abnormal kernel memory growth patterns
- Deploy continuous monitoring of systems using rxrpc authentication mechanisms
- Implement baseline memory usage metrics to detect gradual resource exhaustion
- Schedule periodic system reboots as a temporary mitigation for systems awaiting patches
How to Mitigate CVE-2026-31632
Immediate Actions Required
- Apply the official kernel patches from the Linux kernel stable tree immediately
- Prioritize patching systems that rely heavily on AFS or rxrpc communications
- Consider temporarily disabling rxgk authentication if not critical to operations
- Monitor affected systems for memory exhaustion symptoms until patches are applied
Patch Information
The Linux kernel maintainers have released patches to address this vulnerability. The fix ensures proper cleanup of the rxgk context in all code paths within rxgk_verify_response().
Available patches:
Workarounds
- Implement scheduled system reboots to reclaim leaked memory on critical systems
- Limit access to rxrpc services to trusted users and networks only
- Monitor and alert on memory consumption thresholds to detect exploitation attempts
- Consider disabling the rxgk security mechanism if alternative authentication methods are available
# Check current kernel version for vulnerability status
uname -r
# Monitor kernel memory usage for leak detection
watch -n 60 'cat /proc/meminfo | grep -E "MemFree|Slab|SUnreclaim"'
# Check if rxrpc module is loaded
lsmod | grep rxrpc
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
