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CVE-2026-68159
libceph: bound pg_{temp,upmap,upmap_items} length to CEPH_PG_MAX_SIZE
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem net/ceph. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-68159 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6466-1 · 2026-08-25 · text | 6.12.105-1 | Update the kernel and reboot. DSA-6466-1 shipped the fix on 2026-08-25, in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
__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() ]
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/ceph/osdmap.c
- What this is
- CEPH COMMON CODE (LIBCEPH)MAINTAINERS section matched on net/ceph/ · ceph-devel@vger.kernel.org · Supported
- Kernel module
- libceph
Check it on the machine
grep -w CONFIG_CEPH_LIB /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w libcephPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sid, bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_CEPH_LIB
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-10 (2 months ago)source
- CVSS
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.74%, higher than 53.9% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/ceph
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.13 | 5.10.266 | 66eec4af1e08 |
| 4.13 | 5.15.217 | 4daf06456677 |
| 4.13 | 6.1.184 | d5650ddbd4d4 |
| 4.13 | 6.6.153 | 42bc06c67d94 |
| 4.13 | 6.12.105 | ebdf4b4f3b14 |
| 4.13 | 6.18.46 | 590b07ceea13 |
| 4.13 | 7.1.6 | e36663145abd |
| 4.13 | 7.2 | 9f00f9cf2be2 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DSA-6466-1 | 2026-08-25 | trixie 6.12.105-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:NAttack vector, network
- Malicious pg_temp/pg_upmap data arrives in CEPH_MSG_OSD_MAP from a Ceph monitor or OSD over TCP, is decoded in libceph, and later triggers stack corruption in ceph_pg_to_up_acting_osds during RBD/CephFS/libceph client I/O.
- AC:LAttack complexity, low
- A compromised or attacker-controlled monitor can publish osdmap entries with length >32 for chosen PGs; once the client subscribes, kernel I/O paths such as RBD mount/probe via calc_target deterministically invoke apply_upmap/get_temp_osds and overflow the stack buffer.
- PR:NPrivileges required, none
- Exploitation requires no privileges on the victim host; any machine acting as a Ceph client that receives a forged osdmap from a cluster peer over the network can be attacked without local user capabilities or namespace tricks.
- UI:NUser interaction, none
- No victim user action is needed during exploitation beyond the host already being a Ceph client; forged osdmaps are applied automatically and the overflow fires on subsequent kernel client operations without interactive steps.
- S:UScope, unchanged
- Impact is confined to kernel memory on the Ceph client host (privilege escalation or crash); it does not cross VM, IOMMU, or sandbox boundaries to other security authorities.
- C:HConfidentiality impact, high
- KASAN-confirmed stack out-of-bounds write in ceph_pg_to_up_acting_osds corrupts adjacent stack memory and can be leveraged for arbitrary kernel memory disclosure, not merely a bounded leak.
- I:HIntegrity impact, high
- Unbounded copy loops in apply_upmap() and get_temp_osds() write attacker-controlled u32 OSD IDs past the fixed osds[CEPH_PG_MAX_SIZE] stack array, enabling control-flow hijack and arbitrary kernel writes.
- A:HAvailability impact, high
- The reported reproducer triggers KASAN stack-out-of-bounds followed by kernel BUG in ceph_pg_to_up_acting_osds, demonstrating a reliable kernel oops or panic from malformed osdmap processing on Ceph clients.