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CVE-2026-68131
rbd: Reset positive result codes to zero in object map update path
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem drivers/block. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-68131 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 | fixed | 6.12.101-1 | Update the kernel and reboot. Fixed in 6.12.101-1. 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-4745-1 · 2026-08-18 · text | 6.12.101-1~deb12u1 | Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
In a reply message to an RBD request, a positive result code indicates a data payload, which is not allowed for writes. While rbd_osd_req_callback() already resets a positive result code for writes to zero, rbd_object_map_callback() does not. This allows a corrupted reply to an object map update to trigger the rbd_assert(*result < 0) in __rbd_obj_handle_request(). This happens, because rbd_object_map_callback() calls rbd_obj_handle_request() -> __rbd_obj_handle_request() and passes this positive result code. From __rbd_obj_handle_request(), rbd_obj_advance_write() is called, which leaves the positive result code unchanged and returns true. Therefore, the if(done && *result) branch is executed in __rbd_obj_handle_request() and the assertion triggers. This patch fixes the issue by adjusting the logic in the rbd_object_map_callback() path. A positive result code for an object map update is now reset to zero (similar to rbd_osd_req_callback()), and the message is subsequently handled the same way as if the result code was zero from the beginning. Additionally, a WARN_ON_ONCE() is added for this case.
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.
drivers/block/rbd.c
- What this is
- RADOS BLOCK DEVICE (RBD)MAINTAINERS section matched on drivers/block/rbd.c · ceph-devel@vger.kernel.org · Supported
- Kernel module
- rbd
Check it on the machine
grep -w CONFIG_BLK_DEV_RBD /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 rbdPrints 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_BLK_DEV_RBD
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
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.52%, higher than 43.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/block
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.3 | 5.10.265 | cf1167292f60 |
| 5.3 | 5.15.216 | da926959bf79 |
| 5.3 | 6.1.183 | 6f33d9d539fb |
| 5.3 | 6.6.148 | 14995c4250f0 |
| 5.3 | 6.12.101 | 2419aa740810 |
| 5.3 | 6.18.42 | 34f2a2f32af5 |
| 5.3 | 7.1.6 | b1a613669332 |
| 5.3 | 7.2 | a6c4250b81bd |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DLA-4745-1 | 2026-08-18 | bookworm 6.12.101-1~deb12u1 | 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
- The crash is triggered when libceph processes a crafted MOSDOpReply over the Ceph TCP connection and passes a positive r_result into rbd_object_map_callback(); a compromised or malicious OSD/monitor peer can deliver this without any local syscall on the victim.
- AC:LAttack complexity, low
- An attacker controlling the Ceph OSD can deterministically reply to any object-map update request with a positive result code whenever the mapped image has RBD_FEATURE_OBJECT_MAP and write I/O is in flight, with no race or victim-specific memory layout required.
- PR:NPrivileges required, none
- No privileges on the victim host are needed; exploitation only requires the kernel RBD client to be connected to an attacker-controlled or compromised Ceph cluster, consistent with other libceph client CVE scoring where the remote storage peer drives the bug.
- UI:NUser interaction, none
- After RBD is mapped, object-map updates are driven automatically by block-layer write I/O; no further interactive user action is required at exploit time beyond normal background storage activity on the mapped device.
- S:UScope, unchanged
- The BUG() panic affects only the kernel on the host running the RBD client and does not cross VM, container, or IOMMU security boundaries to another authority.
- C:NConfidentiality impact, none
- The vulnerable path returns immediately on a positive result without decoding reply payload or corrupting memory; impact is limited to an assertion failure with no information disclosure primitive.
- I:NIntegrity impact, none
- No kernel or user data is modified; the positive result code is mishandled and triggers rbd_assert(*result < 0) leading to BUG(), not an arbitrary write or code-execution primitive.
- A:HAvailability impact, high
- RBD_DEBUG is unconditionally defined so rbd_assert() invokes BUG(), causing a kernel panic that fully denies availability on any host with an affected RBD mapping when a malicious OSD reply is received.