# CVE-2026-68159: libceph: bound pg_{temp,upmap,upmap_items} length to CEPH_PG_MAX_SIZE

> A stack out-of-bounds write in the Linux kernel Ceph client allows a malicious monitor to cause memory corruption or denial of service.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Aug 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-95301, BELL-CVE-2026-68159, DEBIAN-CVE-2026-68159, GHSA-83x9-86wr-8vh2, UBUNTU-CVE-2026-68159

## What is CVE-2026-68159?

CVE-2026-68159 is a critical memory corruption vulnerability in Linux, published on 10 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

libceph: bound pg_{temp,upmap,upmap_items} length to CEPH_PG_MAX_SIZE

__decode_pg_temp() decodes an user-controlled length but only rejects
values large enough to overflow the allocation; it does not bound it to
CEPH_PG_MAX_SIZE. The helper backs both pg_temp and pg_upmap decoding, and
apply_upmap()/get_temp_osds() later copy the decoded list into the fixed-size
on-stack array struct ceph_osds.osds[CEPH_PG_MAX_SIZE]. A monitor that sends
an OSDMap with a pg_temp/pg_upmap entry longer than 32 thus causes a stack
out-of-bounds write.

An OSD set for a single PG can never exceed CEPH_PG_MAX_SIZE, so reject longer
entries at decode time. The bound is well below the old overflow threshold, so
it also covers the allocation-size overflow the previous check guarded against.

  BUG: KASAN: stack-out-of-bounds in ceph_pg_to_up_acting_osds
  Write of size 4 ... by task exploit
   kasan_report (mm/kasan/report.c:595)
   ceph_pg_to_up_acting_osds (net/ceph/osdmap.c:2617 net/ceph/osdmap.c:2833)
   calc_target (net/ceph/osd_client.c:1638)
   __submit_request (net/ceph/osd_client.c:2394)
   ceph_osdc_start_request (net/ceph/osd_client.c:2490)
   ceph_osdc_call (net/ceph/osd_client.c:5164)
   rbd_dev_image_probe (drivers/block/rbd.c:6899)
   do_rbd_add (drivers/block/rbd.c:7138)
   ...
  kernel BUG at net/ceph/osdmap.c:2670!

[ idryomov: do the same in __decode_pg_upmap_items() ]

Weakness: CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2026-68159?


## How do I fix CVE-2026-68159?

Apply the vendor's patch.

## Is CVE-2026-68159 being exploited?

There is no known exploitation of CVE-2026-68159 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68159 and fix it if it is affected.

What it is: CVE-2026-68159 is a critical memory corruption vulnerability in Linux, published on 10 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-68159 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-2026-68159/ (Markdown: https://insights.sbomify.com/CVE-2026-68159/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68159
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68159
- OSV: https://osv.dev/vulnerability/CVE-2026-68159

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68159/
Summaries are generated and may contain mistakes; the official description above is the record.