CVE-2026-89731 cxl/ras: Fix cxl_rch_get_aer_info() out-of-bounds AER register read
An out-of-bounds read in the Linux kernel CXL RAS driver allows attackers to leak memory or crash the system via crafted AER register reads.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89731?
CVE-2026-89731 is a high-severity memory corruption vulnerability in Linux, published on 11 Sep 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:
cxl/ras: Fix cxl_rch_get_aer_info() out-of-bounds AER register read
cxl_rch_get_aer_info() copies the RCH Downstream Port AER capability from the RCRB MMIO block using a readl() loop bounded by sizeof(struct aer_capability_regs). This struct is a software layout and its embedded struct pcie_tlp_log is larger than the on-wire AER capability. As a result the loop reads past the mapped AER register block.
The over-read also populates the software-only tail fields including header_log.header_len. An out-of-range header_len passed to pcie_print_tlp_log() can then loop past the header log buffer and cause a second out-of-bounds read.
The read was correct when introduced, but struct pcie_tlp_log has since grown (Header Log and TLP Prefix Log sizes, header_len and flit fields), so sizeof(struct aer_capability_regs) no longer matches the physical AER capability.
Bound the read to the physical AER registers, header through the 16 byte Header Log. Zero the destination first so the software-only fields are deterministic.
Which versions are affected by CVE-2026-89731?
How do I fix CVE-2026-89731?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-89731 being exploited?
There is no known exploitation of CVE-2026-89731 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89731, DEBIAN-CVE-2026-89731, GHSA-qhph-j75q-5546, UBUNTU-CVE-2026-89731.