CVE-2026-90333: dm-integrity: replace forgeable discard filler with a keyed sector marker
dm-integrity: replace forgeable discard filler with a keyed sector marker
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Use the allow_discards_keyed target argument so discarded blocks are marked with a keyed checksum of (salt || sector), computed by integrity_discard_checksum().
dm-integrity allow_discards_keyed = enabled
Event History
Frequently Asked Questions
Who is exposed to this issue?
Systems using dm-integrity in standalone mode with discard support enabled are exposed if an attacker has raw write access to the backing device but does not possess the integrity key.
What does an attacker need to do to bypass integrity verification?
The attacker needs raw write access to the backing device and can replace a block's stored tag with all 0xf6 bytes. The discard-block check then treats the block as discarded and skips HMAC verification.
Does this affect every dm-integrity configuration?
No. The described vulnerable discard handling applies because allow_discards is accepted only in dm-integrity standalone mode.
What configuration change addresses the issue?
Use the new allow_discards_keyed target argument, which marks discarded blocks using a keyed checksum of the salt and sector rather than the forgeable fixed discard filler.