# CVE-2026-72382: ksmbd: reject undersized DACLs before parsing ACEs

> A malicious SMB client can trigger an integer underflow in the Linux kernel's ksmbd module, causing excessive memory allocation and potential denial of service.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72382, DEBIAN-CVE-2026-72382, GHSA-xrhm-hwvc-w6q3, UBUNTU-CVE-2026-72382

## What is CVE-2026-72382?

CVE-2026-72382 is a high-severity vulnerability in Linux, published on 15 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: reject undersized DACLs before parsing ACEs

parse_dacl() limits the attacker-controlled ACE count by comparing it
with the number of minimal ACEs that fit in the DACL size. The DACL size
field is 16 bits, but the expression subtracts sizeof(struct smb_acl).
Because sizeof() is unsigned, a DACL size smaller than the ACL header
underflows to a large size_t.

A malicious client can reach this with:

SMB2_SET_INFO (InfoType=SMB2_O_INFO_SECURITY)
  -> smb2_set_info_sec()
  -> set_info_sec()
  -> parse_sec_desc()
  -> parse_dacl()
     -> init_acl_state(..., 0xffff)
     -> init_acl_state(..., 0xffff)
     -> kmalloc_objs(..., 0xffff)

Thus a malformed security descriptor can make num_aces pass the guard
and drive large temporary ACL state and pointer-array allocations.

Reject DACLs smaller than struct smb_acl before doing the subtraction,
so the ACE count check cannot be bypassed by the underflow.

## Which versions are affected by CVE-2026-72382?


## How do I fix CVE-2026-72382?

Apply the vendor's patch.

## Is CVE-2026-72382 being exploited?

There is no known exploitation of CVE-2026-72382 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72382 and fix it if it is affected.

What it is: CVE-2026-72382 is a high-severity vulnerability in Linux, published on 15 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72382 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-72382/ (Markdown: https://insights.sbomify.com/CVE-2026-72382/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72382
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72382
- OSV: https://osv.dev/vulnerability/CVE-2026-72382

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72382/
Summaries are generated and may contain mistakes; the official description above is the record.