Bug 2536218 (CVE-2026-90333)

Summary: CVE-2026-90333 kernel: dm-integrity: replace forgeable discard filler with a keyed sector marker
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's device-mapper integrity (dm-integrity) target. This vulnerability allows an attacker with raw write access to the backing device, but without the integrity key, to bypass data integrity checks. By stamping any block with a specially crafted discard filler tag, the attacker can make the system treat the block as authentically discarded, leading to a data integrity bypass. This could result in unauthorized data manipulation or corruption.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-09-17 16:58:11 UTC 
In the Linux kernel, the following vulnerability has been resolved:

dm-integrity: replace forgeable discard filler with a keyed sector marker

The discard-block check in dm_integrity_rw_tag() treats a stored tag
of all 0xf6 bytes (DISCARD_FILLER) as proof a block was discarded and
skips HMAC verification. allow_discards is only accepted in
dm-integrity's standalone mode. An attacker with raw write access to
the backing device, but without the integrity key, can stamp any block
with an all-0xf6 tag and have it served as authentic.

Add a new "allow_discards_keyed" target argument that marks discarded
blocks with a keyed checksum of (salt || sector) instead, computed by
integrity_discard_checksum().
Comment 1 gkamathe 2026-09-21 18:56:34 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90333.mbox