ecryptfs: reject oversized encrypted_key_size in parse_tag_3_packet

Overview

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]

Affected

• Linux >= 237fead619984cc48818fe12ee0ceada3f55b012 < 2cd21340163494d312836c77c9fbfe2530b3d075
• Linux >= 237fead619984cc48818fe12ee0ceada3f55b012 < e2152d491ae62d96a32ed59778680a242af1fbc6
• Linux >= 237fead619984cc48818fe12ee0ceada3f55b012 < d2802414081184f79a619ede178aeef3aa989793
• Linux >= 237fead619984cc48818fe12ee0ceada3f55b012 < 33e050cac841498b5175f0f385eee903fd98863c
• Linux >= 237fead619984cc48818fe12ee0ceada3f55b012 < ccd13eff0e7356d2aa28b127b577e4e5ad4563f5
• Linux >= 237fead619984cc48818fe12ee0ceada3f55b012 < 14cb36a500a5a3afbc955dbf69dabc565f1a3b26
• Linux >= 237fead619984cc48818fe12ee0ceada3f55b012 < a419c9ebfc9a40ee56aaad6dc68bfd67d400817b
• Linux >= 237fead619984cc48818fe12ee0ceada3f55b012 < 5babe9c177c364521e3e682b949c5a8c47f4a441
• Linux 2.6.19

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Vendor advisories

• Red Hat VEX · Important · affected: Red Hat Enterprise Linux 6 · updated 2026-09-15 · vex