CVE-2026-98105 in Linux
Summary
by MITRE • 09/25/2026
In the Linux kernel, the following vulnerability has been resolved:
net: ethernet: oa_tc6: Improve the error recovery
When oversubscribed traffic causes lot of buffer overflow errors, probably due to loss of data chunks, driver fails to find a data chunk with end_valid bit set, before it runs out of sk buffer space. As a result, assert is seen during skb_put.
Now, check is made if skb buffer has enough tailroom for the incoming data before accepting. If there is no room, current frame is abandoned and it will start looking for a data chunk with start_valid bit, that is a new frame.
SK buffer allocation error is considered as recoverable error.
rx_buf_overflow flag is too specific and no longer the only condition this flag is used for. Therefore it is renamed as wait_until_start_valid. This is more appropriate as this flag is used to look for the next data chunk with SV bit set, after failures like buffer overflow, buffer allocation failure, skb pointer validity besides buffer overflow error.
Not writing to status0 if it reads 0.
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Analysis
by VulDB Data Team • 09/25/2026
The Linux kernel driver for the OA TC6 Ethernet controller contained a critical flaw in its packet reception logic that could lead to system instability under high network load conditions. The vulnerability manifests when oversubscribed traffic results in significant buffer overflow errors, often accompanied by the loss of data chunks within the incoming stream. In this scenario, the driver's state machine attempts to locate a valid data chunk marked with an end_valid bit set before exhausting the available socket buffer space. When these resources are depleted without finding such a marker, the kernel triggers an assertion failure during the skb_put operation, which typically results in a kernel panic or system crash. This behavior represents a severe availability risk, as normal network congestion can inadvertently bring down the host machine rather than being handled gracefully by the networking stack.
The root cause of this issue lies in insufficient validation of buffer capacity prior to data ingestion and an overly rigid error recovery mechanism that assumes specific bit patterns will always be present within finite buffer limits. The original implementation did not adequately account for scenarios where incoming frames are fragmented or corrupted due to hardware limitations under heavy load, leading the driver to persistently attempt operations on invalid memory regions. By failing to verify whether the socket buffer has sufficient tailroom before accepting new data, the driver risks writing beyond allocated boundaries or triggering assertions that assume valid state transitions which do not occur during overflow events. This lack of defensive programming against resource exhaustion is a common pattern in low-level network drivers where performance optimization sometimes overshadows robustness checks.
To resolve this vulnerability, the patch introduces several key improvements to the error recovery logic and buffer management strategies. First, the driver now explicitly checks if the socket buffer possesses adequate tailroom for incoming data before proceeding with acceptance. If sufficient space is unavailable, the current frame is abandoned, allowing the system to reset its search state and look for a new data chunk identified by the start_valid bit rather than continuing to process potentially corrupted or incomplete frames. This approach ensures that transient resource constraints do not propagate into fatal kernel errors but are instead treated as recoverable conditions requiring state re-synchronization with the incoming stream.
Additionally, the patch refactors internal flag usage to better reflect its operational purpose and scope. The rx_buf_overflow flag was renamed to wait_until_start_valid because it serves a broader function beyond just handling buffer overflow scenarios. This new naming convention accurately describes its role in locating the next valid data chunk marked with the start_valid bit after various failure modes, including buffer allocation failures, invalid socket buffer pointers, and overflow errors. By generalizing this state indicator, the code becomes more maintainable and logically consistent across different error paths. Furthermore, a minor but important fix prevents writing to status0 if it reads as zero, avoiding unnecessary or potentially harmful register writes that could interfere with hardware operation or driver stability.
From a security perspective, this vulnerability aligns with CWE-401, which describes the lack of release of memory after successful allocation leading to resource exhaustion, and CWE-252, concerning unchecked return values where failure conditions are not properly handled. The exploitation vector primarily involves network-based denial-of-service attacks that aim to saturate the interface or induce specific packet patterns that trigger buffer overflows in the driver's receive path. Attackers could potentially craft packets designed to maximize fragmentation or delay acknowledgments to force the driver into states where it cannot find valid end markers, thereby inducing kernel panics and disrupting service availability.
Mitigation strategies should focus on both immediate patching and long-term architectural improvements. Administrators must apply the latest kernel updates that include this specific fix for the OA TC6 Ethernet driver to prevent assertion failures under load. Network operators should also consider implementing rate limiting or traffic shaping policies at upstream switches to reduce the likelihood of oversubscription events reaching the host interface during peak times. For developers, adhering to strict buffer validation protocols before any memory manipulation is essential, and utilizing ATT&CK technique T1498, specifically network denial of service via resource exhaustion, can help in designing monitoring rules that detect abnormal traffic patterns indicative of such exploitation attempts. Continuous integration testing with fuzzed network inputs remains a best practice for identifying similar edge cases in low-level driver code before they reach production environments.