CVE-2026-31658: 
Linux Kernel vulnerability analysis and mitigation

CVE-2026-31658 is a memory leak vulnerability in the Linux kernel's Altera TSE (Triple Speed Ethernet) network driver. When dma_map_single() fails during packet transmission in the tse_start_xmit() function, the function returns NETDEV_TX_OK without freeing the socket buffer (skb), causing a memory leak on every DMA mapping failure. The vulnerability affects Linux kernel versions from 3.15 through multiple stable branches up to 6.19.12 and 7.0-rc7. It was published on April 24, 2026, and carries a CVSS v3.1 base score of 5.5 (Medium) (GitHub Advisory, Feedly).

The root cause is classified as CWE-772 (Missing Release of Resource after Effective Lifetime) and CWE-401 (Missing Release of Memory after Effective Lifetime). In tse_start_xmit(), when dma_map_single() fails to map a transmit buffer, the error path returns NETDEV_TX_OK — signaling to the network stack that the packet was successfully consumed — without calling dev_kfree_skb_any() to release the skb. This means the kernel's network stack never reclaims the socket buffer, resulting in a persistent memory leak for each DMA mapping failure. The fix adds a dev_kfree_skb_any() call before the erroneous return to properly release the skb (GitHub Advisory, Feedly).

The primary impact is availability: repeated DMA mapping failures cause gradual memory exhaustion that can accumulate to trigger out-of-memory (OOM) conditions, system instability, and potential kernel crashes. In high-traffic network environments or systems with frequent DMA failures, the leak can accumulate rapidly enough to cause denial of service. There is no confidentiality or integrity impact, and the vulnerability is limited to systems running the Altera TSE driver (Feedly).

There is no public proof-of-concept exploit and no evidence of in-the-wild exploitation as of the time of publication (Feedly). The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. The EPSS score is approximately 0.024%, reflecting a very low probability of exploitation in the near term. Exploitation requires local access with low privileges and depends on triggering DMA mapping failures, which limits practical exploitability to specific hardware and workload conditions.

• Logs: Kernel logs (dmesg or /var/log/kern.log) showing repeated DMA mapping failure messages from the altera_tse driver (e.g., altera_tse: DMA mapping error).
• System Metrics: Gradual, unexplained decrease in available system memory (/proc/meminfo showing declining MemFree/MemAvailable) on systems using the Altera TSE network interface, without a corresponding increase in application memory usage.
• OOM Events: Out-of-memory killer invocations logged in kernel messages (oom-kill entries in dmesg) on systems with the Altera TSE driver under network load.

Update the Linux kernel to a patched stable release. Fixed versions include: 5.10.253, 5.15.203, 6.1.169, 6.6.135, 6.12.82, 6.18.23, 6.19.13, and 7.0 (stable). Multiple stable branch patches are available via git.kernel.org. As a temporary workaround, reducing network traffic on affected systems can limit the frequency of DMA mapping failures and slow memory exhaustion. Monitor systems for OOM conditions as an indicator of active impact (GitHub Advisory, Red Hat Bugzilla, SUSE Advisory).