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CVE-2026-89607
ecryptfs: reject oversized encrypted_key_size in parse_tag_3_packet
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-2026-89607 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
parse_tag_3_packet() set encrypted_key_size from the Tag 3 packet body without bounding it against ECRYPTFS_MAX_KEY_BYTES (64). When encrypted_key_size > 64, decrypt_passphrase_encrypted_session_key() sets decrypted_key_size = encrypted_key_size and performs two out-of-bounds writes: 1. crypto_skcipher_decrypt() writes encrypted_key_size bytes into decrypted_key[64] via scatterlist, overflowing into the parent ecryptfs_auth_tok struct. 2. memcpy(crypt_stat->key, decrypted_key, decrypted_key_size) writes into crypt_stat->key[64], corrupting root_iv, keysig_list, and mutexes in ecryptfs_crypt_stat. Only AES-192 (cipher code 0x08) enables this because it sets crypt_stat->key_size = 24 independently of encrypted_key_size, allowing crypto_skcipher_setkey() to succeed while encrypted_key_size exceeds ECRYPTFS_MAX_KEY_BYTES. The PKI decryption path (parse_tag_65_packet) already validates decrypted_key_size <= ECRYPTFS_MAX_KEY_BYTES; the passphrase path omits this check. Bound encrypted_key_size against ECRYPTFS_MAX_KEY_BYTES (64) rather than ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES (512). The 64-byte limit also protects the 512-byte encrypted_key[] buffer, so the former 512-byte check is removed as redundant. [tyhicks: Adjust the code comment to refer to macros representing the buffer sizes rather than mentioning the buffer size values since they may change in the future]
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
- 0.17%, 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 |
|---|---|---|
| 2.6.19 | 5.10.270 | 2cd213401634 |
| 2.6.19 | 5.15.221 | e2152d491ae6 |
| 2.6.19 | 6.1.188 | d28024140811 |
| 2.6.19 | 6.6.157 | 33e050cac841 |
| 2.6.19 | 6.12.109 | ccd13eff0e73 |
| 2.6.19 | 6.18.50 | 14cb36a500a5 |
| 2.6.19 | 7.2.4 | a419c9ebfc9a |
| 2.6.19 | 7.3 | 5babe9c177c3 |
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
- Triggered by a local open/setattr on an eCryptfs mount: ecryptfs_open -> read_or_initialize_metadata -> ecryptfs_read_metadata parses attacker-supplied Tag 3 packets from the lower file header (or xattr). The kernel does not process this as network protocol data.
- AC:LAttack complexity, low
- The attacker fully controls the Tag 3 body, including AES-192 cipher code 0x08 and an AES-block-aligned encrypted_key_size of 80-512 bytes. decrypt_passphrase_encrypted_session_key() then overflows deterministically; no race or uninfluenced memory layout is required to trigger the writes.
- PR:LPrivileges required, low
- An unprivileged user reaches this on standard eCryptfs deployments (setuid-root mount.ecryptfs_private and per-user encrypted home/Private). They plant a crafted lower file under their own .Private directory and open it through the already-mounted eCryptfs tree; init-namespace root is not required.
- UI:NUser interaction, none
- The attacker performs the whole sequence themselves: install a matching passphrase auth token, write the malformed Tag 3/Tag 11 header into their lower directory, and open the file. No action by another user is required.
- S:UScope, unchanged
- The out-of-bounds writes corrupt kernel heap and eCryptfs inode-private objects in the same kernel security authority. This is local privilege escalation, not a VM, IOMMU, or sandbox boundary crossing.
- C:HConfidentiality impact, high
- crypto_skcipher_decrypt() and memcpy() write tens to hundreds of bytes past decrypted_key[64] and crypt_stat->key[64], overflowing into reserved/token fields, keysig_list, mutexes, and adjacent slab/inode-cache objects. That heap corruption can be groomed into an arbitrary kernel read.
- I:HIntegrity impact, high
- Session-key wrap uses AES-ECB with the attacker's known passphrase-derived key, so the overflow payload is chosen plaintext. Up to 448 bytes past the 64-byte buffers corrupt list_head pointers and neighboring slab objects, yielding a write primitive for control-flow hijack.
- A:HAvailability impact, high
- Corrupting keysig_list, embedded mutexes, and adjacent inode-cache/slab objects causes kernel oops or panic. The attacker can open the crafted file repeatedly to crash the system at will.