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CVE-2026-89609
ecryptfs: hold msg ctx list lock when cleaning daemon queue
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-2026-89609 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_exorcise_daemon() drops queued messages from a dying daemon without holding ecryptfs_msg_ctx_lists_mux, but ecryptfs_msg_ctx_alloc_to_free() requires that lock. Take the list lock while moving the queued contexts back to the free list to avoid racing with other global msg ctx list users.
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
- 0.18%, higher than 6.7% 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 | 64d8998e36cf |
| 2.6.26 | 5.15.221 | 4d50b8aea11a |
| 2.6.26 | 6.1.188 | 956541efd125 |
| 2.6.26 | 6.6.157 | ec1627bcb5b5 |
| 2.6.26 | 6.12.109 | 7e48afafe7ab |
| 2.6.26 | 6.18.50 | 0d9636ecba34 |
| 2.6.26 | 7.2.4 | 4c02acbe0a26 |
| 2.6.26 | 7.3 | 779972513c2f |
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 missing lock is reached only via local syscalls: close() of /dev/ecryptfs runs ecryptfs_miscdev_release() into ecryptfs_exorcise_daemon(), racing PKI open/create that calls ecryptfs_wait_for_response(); no network or adjacent protocol path exists.
- AC:LAttack complexity, low
- The attacker owns both sides of the race: one thread does PKI file ops so wait_for_response() list_move()s a msg_ctx under ecryptfs_msg_ctx_lists_mux, while another closes /dev/ecryptfs so exorcise_daemon() list_move()s the same or sibling nodes without that lock.
- PR:LPrivileges required, low
- ecryptfs_miscdev_open() has no capability check; daemons are per-euid. An unprivileged user reaches this by running ecryptfsd on /dev/ecryptfs and using an eCryptfs mount from setuid mount.ecryptfs_private or an 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/close syscalls; no other user needs to mount, open a file, or otherwise interact.
- S:UScope, unchanged
- Corrupted global msg_ctx lists and the double-free of msg_ctx->msg 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
- Unlocked list_move() of a queued msg_ctx racing wait_for_response() is a use-after-free of the kmalloc'd message buffer and leaves corrupted global list pointers that can be groomed to disclose kernel memory.
- I:HIntegrity impact, high
- The same race is a heap double-free of msg_ctx->msg plus unsynchronized list_move() writes through corrupted next/prev pointers, a classic memory-corruption primitive usable for control-flow hijacking.
- A:HAvailability impact, high
- Concurrent unlocked list_move() readily oopses on LIST_POISON or a general protection fault during later list walks, and the double-free of msg_ctx->msg can panic the kernel.