Bug 2502396 (CVE-2026-63893)

Summary: CVE-2026-63893 kernel: thunderbolt: property: Reject u32 wrap in tb_property_entry_valid()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Thunderbolt property handling. A remote attacker, by acting as a malicious XDomain peer, could craft a special property entry that causes an integer overflow when calculating memory access. This overflow allows the system to read memory outside of the intended buffer, leading to information disclosure through device name or vendor name system attributes. This vulnerability could expose sensitive, untargeted data.
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Description OSIDB Bzimport 2026-07-19 16:05:57 UTC 
In the Linux kernel, the following vulnerability has been resolved:

thunderbolt: property: Reject u32 wrap in tb_property_entry_valid()

entry->value is u32 and entry->length is u16; the sum is performed in
u32 and wraps.  A malicious XDomain peer can pick
value = 0xffffff00, length = 0x100 so the sum 0x100000000 wraps to 0
and passes the > block_len check.  tb_property_parse() then passes
entry->value to parse_dwdata() as a dword offset into the property
block, reading attacker-directed memory far past the allocation.

For TEXT-typed entries with the "deviceid" or "vendorid" keys this
lands in xd->device_name / xd->vendor_name and is readable back via
the per-XDomain device_name / vendor_name sysfs attributes; the leak
is NUL-bounded (kstrdup() stops at the first zero byte) and
untargeted (the attacker picks a delta, not an absolute address).
DATA-typed entries are parsed into property->value.data but not
generically surfaced to userspace.

Use check_add_overflow() so a wrapped sum is rejected.
Comment 1 Keith Grant 2026-07-21 20:25:40 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026071942-CVE-2026-63893-aa7f@gregkh/T