Bug 2513165 (CVE-2026-68159)

Summary: CVE-2026-68159 kernel: Linux kernel: libceph stack out-of-bounds write via crafted OSDMap
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in libceph in the Linux kernel. A remote attacker, acting as a malicious monitor, could send a specially crafted OSDMap (Object Storage Device Map) with an overly long pg_temp or pg_upmap entry. This could lead to a stack out-of-bounds write, resulting in a kernel bug and potentially a denial of service.
Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-08-10 12:22:49 UTC
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() ]