CVE-2026-46110

What it is

In the Linux kernel, the following vulnerability has been resolved: net: stmmac: Prevent NULL deref when RX memory exhausted The CPU receives frames from the MAC through conventional DMA: the CPU allocates buffers for the MAC, then the MAC fills them and returns ownership to the CPU. For each hardware RX queue, the CPU and MAC coordinate through a shared ring array of DMA descriptors: one descriptor per DMA buffer. Each descriptor includes the buffer's physical address and a status flag ("OWN") indicating which side owns the buffer: OWN=0 for CPU, OWN=1 for MAC. The CPU is only allowed to set the flag and the MAC is only allowed to clear it, and both must move through the ring in sequence: thus the ring is used for both "submissions" and "completions." In the stmmac driver, stmmac_rx() bookmarks its position in the ring with the `cur_rx` index. The main receive loop in that function checks for rx_descs[cur_rx].own=0, gives the corresponding buffer to the network stack (NULLing the pointer), and increments `cur_rx` modulo the ring size. After the loop exits, stmmac_rx_refill(), which bookmarks its position with `dirty_rx`, allocates fresh buffers and rearms the descriptors (setting OWN=1). If it fails any allocation, it simply stops early (leaving OWN=0) and will retry where it left off when next called. This means descriptors have a three-stage lifecycle (terms my own): - `empty` (OWN=1, buffer valid) - `full` (OWN=0, buffer valid and populated) - `dirty` (OWN=0, buffer NULL) But because stmmac_rx() only checks OWN, it confuses `full`/`dirty`. In the past (see 'Fixes:'), there was a bug where the loop could cycle `cur_rx` all the way back to the first descriptor it dirtied, resulting in a NULL dereference when mistaken for `full`. The aforementioned commit resolved that *specific* failure by capping the loop's iteration limit at `dma_rx_size - 1`, but this is only a partial fix: if the previous stmmac_rx_refill() didn't complete, then there are leftover `dirty` descriptors that the loop might encounter without needing to cycle fully around. The current code therefore panics (see 'Closes:') when stmmac_rx_refill() is memory-starved long enough for `cur_rx` to catch up to `dirty_rx`. Fix this by explicitly checking, before advancing `cur_rx`, if the next entry is dirty; exit the loop if so. This prevents processing of the final, used descriptor until stmmac_rx_refill() succeeds, but fully prevents the `cur_rx == dirty_rx` ambiguity as the previous bugfix intended: so remove the clamp as well. Since stmmac_rx_zc() is a copy-paste-and-tweak of stmmac_rx() and the code structure is identical, any fix to stmmac_rx() will also need a corresponding fix for stmmac_rx_zc(). Therefore, apply the same check there. In stmmac_rx() (not stmmac_rx_zc()), a related bug remains: after the MAC sets OWN=0 on the final descriptor, it will be unable to send any further DMA-complete IRQs until it's given more `empty` descriptors. Currently, the driver simply *hopes* that the next stmmac_rx_refill() succeeds, risking an indefinite stall of the receive process if not. But this is not a regression, so it can be addressed in a future change.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of service disruption.

Exploit odds

0.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-05-28 10:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-15 02:19 UTC Last updatedMost recent change to the record

Details

Published

2026-05-28 10:16 UTC

Last modified

2026-10-15 02:19 UTC

Exploit probability

0.5% · EPSS, next 30 days

Weakness

CWE-476 · NULL pointer dereference

Record status

Undergoing Analysis

Affected

• Linux Kernel < 6.1.176
• Linux Kernel < 6.6
• Linux Kernel < 6.6.140
• Linux Kernel < 6.12.88
• Linux Kernel < 6.18.30
• Linux Kernel < 7.0.7
• Linux Kernel 6.7
• Linux Kernel 7.1

Attack profile CVSS 3.1 · 7.5

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-46110.md and follow it. Check whether this project is affected by CVE-2026-46110. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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