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CVE-2026-74376
md/raid10: reset read_slot when reusing r10bio for discard
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem drivers/md. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-74376 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 | fixed | 6.1.180-1 | Update the kernel and reboot. Fixed in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
put_all_bios() always drops devs[i].bio, but it only drops devs[i].repl_bio when r10_bio->read_slot < 0. If discard reuses an r10bio that was previously used for a read, read_slot can still be non-negative, and discard cleanup can skip bio_put() on repl_bio. Reset read_slot to -1 when preparing an r10bio for discard so the replacement bio is always released correctly.
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/md/raid10.c
- What this is
- SOFTWARE RAID (Multiple Disks) SUPPORTMAINTAINERS section matched on drivers/md/raid* · linux-raid@vger.kernel.org · Supported
- Kernel module
- raid10
Check it on the machine
grep -wE 'CONFIG_MD|CONFIG_MD_RAID10' /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 raid10Prints 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, sidm
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switches
- CONFIG_MD, CONFIG_MD_RAID10
- Reads as
- all on means the file is compiled; any one off means it is not.
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
- 2026-08-15 (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
- 0.50%, higher than 41.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/md
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.13 | 5.15.212 | 3cb2a606ce49 |
| 5.13 | 6.1.178 | 561c9711e4f5 |
| 5.13 | 6.6.145 | ce3030e92f14 |
| 5.13 | 6.12.97 | 742e4afd247d |
| 5.13 | 6.18.40 | b7313f23ea5a |
| 5.13 | 7.1.5 | eb04e3e9c14e |
| 5.13 | 7.2 | 6b8a26af065d |
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
- iSCSI/NVMe-oF targets and appliances commonly expose RAID10-backed LUNs; remote SCSI UNMAP maps through target_core iblock_execute_unmap()/blkdev_issue_discard() to md_handle_request() and raid10_handle_discard without local access.
- AC:LAttack complexity, low
- The attacker controls both pool poisoning reads and triggering discards; mempool-reused r10bios retain a non-negative read_slot from prior reads, so each qualifying discard reliably skips repl_bio bio_put() when replacement mirrors exist.
- PR:NPrivileges required, none
- Network UNMAP from an iSCSI/NVMe-oF client needs no Linux UID or capabilities on the target; local exploitation only needs O_RDWR on the md device or FITRIM (CAP_SYS_ADMIN, obtainable in user namespaces), both below High.
- UI:NUser interaction, none
- No interactive victim action—exploitation uses normal block-layer discard requests (fstrim cron, UNMAP, BLKDISCARD) issued or scripted by the attacker without cooperation.
- S:UScope, unchanged
- The bug corrupts/leaks kernel bio objects within the same host kernel security domain; it does not cross VM, container, or IOMMU boundaries.
- C:HConfidentiality impact, high
- Stale read_slot misclassifies repl_bio as rdev in the r10dev union during put_all_bios(), leaking live bios holding kernel pointers and enabling heap-grooming read primitives; scored High when uncertain per memory-corruption guidance.
- I:HIntegrity impact, high
- The read_slot/repl_bio union type confusion skips bio_put() on attacker-submitted replacement discard clones, enabling slab manipulation for arbitrary kernel writes; type confusion maps to High integrity impact per kernel CVSS guidance.
- A:HAvailability impact, high
- Repeated read-then-discard cycles leak bios on every hit; on busy RAID10 storage servers this exhausts kmem and can trigger OOM killer or panic, so Availability is High rather than Low per the conservative rule.