CVE-2026-63893 thunderbolt: property: Reject u32 wrap in tb_property_entry_valid()
A malicious Thunderbolt peer can trigger an integer overflow to read out-of-bounds kernel memory, leaking device information via sysfs attributes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-63893?
CVE-2026-63893 is a high-severity vulnerability in Linux kernel, published on 19 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-190
Which versions are affected by CVE-2026-63893?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-63893?
Apply the vendor's patch.
Is CVE-2026-63893 being exploited?
There is no known exploitation of CVE-2026-63893 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-63893, DEBIAN-CVE-2026-63893, GHSA-x965-jq5m-mrm4, ROOT-OS-UBUNTU-2204-CVE-2026-63893, UBUNTU-CVE-2026-63893.