CVE-2026-29642

Description

A local attacker who can execute privileged CSR operations (or can induce firmware to do so) performs carefully crafted reads/writes to menvcfg (e.g., csrrs in M-mode). On affected XiangShan versions (commit aecf601e803bfd2371667a3fb60bfcd83c333027, 2024-11-19), these menvcfg accesses can unexpectedly set WPRI (reserved) bits in the status view (xstatus) to 1. RISC-V defines WPRI fields as "writes preserve values, reads ignore values," i.e., they must not be modified by software manipulating other fields, and menvcfg itself contains multiple WPRI fields.

References

• https://docs.riscv.org/reference/isa/priv/machine.html
• https://docs.riscv.org/reference/isa/priv/priv-csrs.html
• https://github.com/OpenXiangShan/XiangShan/commit/5e3dd63
• https://github.com/OpenXiangShan/XiangShan/issues/3934