Look up another CVE · open CVE-2026-89606 in the interactive tracker
CVE-2026-89606
ecryptfs: reject too-small tag 70 packets
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-2026-89606 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_parse_tag_70_packet() subtracts fixed metadata fields from the parsed packet body size to derive the encrypted filename size. A malformed packet with a body smaller than those fixed fields can underflow that size calculation. Reject tag 70 packets before the subtraction unless the body contains the signature, cipher code, and at least one byte of encrypted filename data.
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/keystore.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 -w CONFIG_ECRYPT_FS /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 switch
- CONFIG_ECRYPT_FS
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
- 0.14%, higher than 2.9% 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 |
|---|---|---|
| 2.6.29 | 5.10.270 | df5f375a6151 |
| 2.6.29 | 5.15.221 | 5668121974eb |
| 2.6.29 | 6.1.188 | 2e5afed9503d |
| 2.6.29 | 6.6.157 | 414a0f04feb0 |
| 2.6.29 | 6.12.109 | 9d88391bbed7 |
| 2.6.29 | 6.18.50 | b31da1ecf139 |
| 2.6.29 | 7.2.4 | d2869768eab5 |
| 2.6.29 | 7.3 | e97bbe1b2bd8 |
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 through local VFS operations on an eCryptfs mount with filename encryption: getdents via ecryptfs_filldir() and readlink via ecryptfs_get_link(), which decode lower-filesystem names or symlink targets into tag 70 packets. No network protocol or remote peer data is parsed.
- AC:LAttack complexity, low
- An attacker who can create names on the lower filesystem fully controls the tag-70 length byte and can copy a valid FNEK signature from their own mount or existing encrypted names, so the unsigned size wrap is deterministic with no race or uninfluenced condition.
- PR:LPrivileges required, low
- Unprivileged users reach this on standard eCryptfs deployments (encrypted home/Private via setuid mount.ecryptfs_private, or an already-mounted per-user eCryptfs directory) by writing the lower directory they own; triggering does not require init-namespace root.
- UI:NUser interaction, none
- The attacker plants the malformed ECRYPTFS_FNEK_ENCRYPTED name or lower symlink target and then issues getdents or readlink on their own eCryptfs mount; no separate victim action is required, and in the encrypted-home case the mount already exists at login.
- S:UScope, unchanged
- Memory corruption and oops stay inside the host kernel's eCryptfs/VFS context. This is ordinary kernel impact, not a VM, IOMMU, or sandbox-boundary escape.
- C:HConfidentiality impact, high
- The underflowed block_aligned_filename_size is used as the scatterlist, kmalloc, and skcipher-decrypt length for the encrypted filename, so a wrapped length becomes an out-of-bounds read of kernel memory adjacent to the decoded packet buffer.
- I:HIntegrity impact, high
- The same wrapped length is the destination size for kmalloc plus crypto_skcipher_decrypt and the subsequent memcpy of the decrypted name, yielding an out-of-bounds write into heap/crypto scratch buffers that can be used for control-flow hijack.
- A:HAvailability impact, high
- virt_to_scatterlist() returns 0 for the wrapped size without the caller setting rc, so parse_tag_70_packet() returns success with a NULL filename; ecryptfs_get_link() then does buf[len]='\0' on that NULL pointer and oopses the kernel.