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CVE-2026-89605
ecryptfs: release message context on send failure
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem fs/ecryptfs. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89605 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-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
ecryptfs_send_message_locked() moves a message context from the free list to the allocated list before sending the request to the userspace daemon. If ecryptfs_send_miscdev() fails, the context is left on the allocated list and cannot be reused. Move it back to the free list on failure and clear the caller's pointer.
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.
fs/ecryptfs/messaging.c
- What this is
- ECRYPT FILE SYSTEMMAINTAINERS section matched on fs/ecryptfs/ · ecryptfs@vger.kernel.org · Odd Fixes
- Kernel module
- ecryptfs
Check it on the machine
grep -wE 'CONFIG_ECRYPT_FS|CONFIG_ECRYPT_FS_MESSAGING' /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 ecryptfsPrints 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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookworm, trixie, forky, sid, bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_ECRYPT_FS, CONFIG_ECRYPT_FS_MESSAGING
- 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
- 2026-09-11 (37 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/ecryptfs
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.26 | 5.10.270 | 177e0c32fec3 |
| 2.6.26 | 5.15.221 | 743e7aeb9575 |
| 2.6.26 | 6.1.188 | 590fc6140e29 |
| 2.6.26 | 6.6.157 | 30845ed22747 |
| 2.6.26 | 6.12.109 | 47ce611cb13f |
| 2.6.26 | 6.18.50 | 9319706316a8 |
| 2.6.26 | 7.2.4 | 654b7e79443f |
| 2.6.26 | 7.3 | 219644a3ad55 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | 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:LAttack vector, local
- The bug is reached only via local syscalls: open/creat on an eCryptfs mount drives pki_encrypt_session_key()/decrypt_pki_encrypted_session_key() into ecryptfs_send_message_locked(), and the per-euid daemon is registered with open(/dev/ecryptfs); no network or adjacent protocol path exists.
- AC:LAttack complexity, low
- ecryptfs_send_miscdev() fails only on kmalloc(), which a local attacker in a memory cgroup can force by filling memory.max so the small GFP_KERNEL allocation returns NULL; the attacker then repeats create/open while running the daemon, with no race or other condition outside their control.
- PR:LPrivileges required, low
- Neither miscdev_open() nor the PKI send path checks capabilities. An unprivileged user reaches this by running ecryptfsd on /dev/ecryptfs and using an eCryptfs mount from setuid mount.ecryptfs_private or an existing encrypted home, with a user-keyring PRIVATE_KEY auth token.
- UI:NUser interaction, none
- The attacker registers their own daemon, installs their own auth token, uses their own eCryptfs directory, and issues the create/open syscalls; no other user needs to mount, open a file, or otherwise interact.
- S:UScope, unchanged
- The leaked msg_ctx slots and any later use of the dangling msg_ctx->task pointer stay inside the host kernel's eCryptfs messaging subsystem; this is ordinary kernel impact, not a VM, IOMMU, or sandbox escape.
- C:HConfidentiality impact, high
- A failed send leaves the msg_ctx PENDING with a raw task_struct pointer. After the sender exits, the attacker's daemon can write a MSG_RESPONSE with that index and predictable counter so ecryptfs_process_response() calls wake_up_process() on the freed task, a UAF that discloses kernel memory.
- I:HIntegrity impact, high
- The same task_struct use-after-free is heap-sprayable: wake_up_process() writes into a recycled task object and can hijack control flow. Stuck PENDING contexts are also never returned to the 32-slot global pool, breaking eCryptfs messaging for every user.
- A:HAvailability impact, high
- Each failed send permanently removes one of 32 global msg_ctx slots from the free list until reboot, fully denying eCryptfs PKI wrap/unwrap for all users, and the dangling-task wake_up_process() path can oops or panic the kernel.