In the Linux kernel, the following vulnerability has been resolved:
arm64: mte: Avoid setting PG_mte_tagged if no tags cleared or restored
Prior to commit 69e3b846d8a7 ("arm64: mte: Sync tags for pages where PTE
is untagged"), mte_sync_tags() was only called for pte_tagged() entries
(those mapped with PROT_MTE). Therefore mte_sync_tags() could safely use
test_and_set_bit(PG_mte_tagged, &page->flags) without inadvertently
setting PG_mte_tagged on an untagged page.
The above commit was required as guests may enable MTE without any
control at the stage 2 mapping, nor a PROT_MTE mapping in the VMM.
However, the side-effect was that any page with a PTE that looked like
swap (or migration) was getting PG_mte_tagged set automatically. A
subsequent page copy (e.g. migration) copied the tags to the destination
page even if the tags were owned by KASAN.
This issue was masked by the page_kasan_tag_reset() call introduced in
commit e5b8d9218951 ("arm64: mte: reset the page tag in page->flags").
When this commit was reverted (20794545c146), KASAN started reporting
access faults because the overriding tags in a page did not match the
original page->flags (with CONFIG_KASAN_HW_TAGS=y):
BUG: KASAN: invalid-access in copy_page+0x10/0xd0 arch/arm64/lib/copy_page.S:26
Read at addr f5ff000017f2e000 by task syz-executor.1/2218
Pointer tag: [f5], memory tag: [f2]
Move the PG_mte_tagged bit setting from mte_sync_tags() to the actual
place where tags are cleared (mte_sync_page_tags()) or restored
(mte_restore_tags()).
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
- EG Severity
- Not assessed: no CVSS publishedA missing CVSS is not a severity of zero.
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-26). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- No SSVC decision: EchelonGraph has not assessed this CVECISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the BOD 26-04 block below.
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it