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CVE-2026-89608
ecryptfs: pass packet set buffer size to parser
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-2026-89608 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_packet_set() receives a pointer into the file header, but it calculates the remaining packet buffer size from PAGE_SIZE - 8. For version 1 headers the packet set starts later in the header, so this can overstate the available buffer. Pass the actual packet set buffer length from the caller and calculate per-packet limits from the remaining bytes in that buffer. Recompute the remaining length after consuming a tag 3 packet before parsing the following tag 11 packet.
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/crypto.c
fs/ecryptfs/ecryptfs_kernel.h
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
- 7.1 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.16%, higher than 5.3% 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 |
|---|---|---|
| 2.6.19 | 5.10.270 | e7573b0e3058 |
| 2.6.19 | 5.15.221 | 66a87559ecb2 |
| 2.6.19 | 6.1.188 | 3bd9bb3e167a |
| 2.6.19 | 6.6.157 | 749fa08d8f1b |
| 2.6.19 | 6.12.109 | 329de8b9e988 |
| 2.6.19 | 6.18.50 | e5d254e654f2 |
| 2.6.19 | 7.2.4 | 747fd45be396 |
| 2.6.19 | 7.3 | 2602b79c5b3e |
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 over-read is reached only by a local open or setattr on an eCryptfs mount (ecryptfs_open/ecryptfs_setattr → ecryptfs_read_metadata → ecryptfs_parse_packet_set) which parses the attacker-supplied lower-file header or xattr; this is not a network protocol path.
- AC:LAttack complexity, low
- Opening a crafted eCryptfs file deterministically feeds attacker-controlled version-1 headers and Tag 1/3/11 lengths into parse_packet_set(), which then uses an overstated PAGE_SIZE-8 bound; no race or uninfluenced memory layout is required.
- PR:LPrivileges required, low
- An unprivileged user reaches this on standard eCryptfs deployments (setuid-root mount.ecryptfs_private and per-user encrypted home/Private) by planting a crafted file in their own lower directory and opening it through the already-mounted tree; init-namespace root is not required.
- UI:NUser interaction, none
- The attacker writes the malformed header into their lower directory and opens the corresponding eCryptfs file themselves; no action by another user is required.
- S:UScope, unchanged
- The out-of-bounds header-slab read and any resulting oops stay inside the host kernel eCryptfs code; this is not a VM escape, IOMMU bypass, or other cross-authority breakout.
- C:HConfidentiality impact, high
- parse_packet_set() treats PAGE_SIZE-8 as the packet-set limit even after the version-1 header advances the pointer, and Tag 11 is parsed with the pre-Tag-3 remainder so max_packet_size can underflow; subsequent Tag 1 copies up to 512 bytes from adjacent slab/pages, an OOB read rated High unless a few bytes.
- I:NIntegrity impact, none
- Packet parsers memcpy into size-checked destinations (encrypted_key[], sig_tmp_space[8]); this bug is a source over-read of the PAGE_SIZE header cache object, not an out-of-bounds write, UAF, or control-flow hijack primitive.
- A:HAvailability impact, high
- After the size_t remainder underflows, src[i] and later memcpy() walk off the header cache object into adjacent or unmapped pages and can oops; the attacker can reopen the crafted file to crash the host at will.