XiangShan (Open-source high-performance RISC-V processor) commit edb1dfaf7d290ae99724594507dc46c2c2125384 (2024-11-28) contains an improper exceptional-condition handling flaw in its CSR subsystem (NewCSR). On affected versions, certain sequences of CSR operations targeting non-existent/custom CSR addresses may trigger an illegal-instruction exception but fail to reliably transfer control to the configured trap handler (mtvec), causing control-flow disruption and potentially leaving the core in a hung or unrecoverable state. This can be exploited by a local attacker able to execute code on the processor to cause a denial of service and potentially inconsistent architectural state.
CVE-2026-29643
Score 7.1 from GitHub Security Advisory (severity: HIGH) published 2026-04-21. NVD baseline CVSS 7.1; sources differ by 0.0.
- High severity, but no confirmed exploitation yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.1
- EG Score
- 7.1(medium)
- EG Risk
- —
- EPSS
- 6.1%
- KEV
- Not listed
Published
April 20, 2026
Last Modified
April 21, 2026
Advisory Details (4)
Auto-updated Jun 14, 2026Unable to Handle Specific Sequences of Illegal Instructions · Issue #3959 · OpenXiangShan/XiangShan · GitHub
https://github.com/OpenXiangShan/XiangShan/issues/3959fix(CSR): fix shadow writing for custom PMA CSRs not in `csrRwMap`
Fix merged in OpenXiangShan/XiangShan PR #3966 on 2024-12-01 — awaiting tagged release
https://github.com/OpenXiangShan/XiangShan/pull/3966Untitled :: RISC-V Ratified Specifications Library
https://docs.riscv.org/reference/isa/priv/priv-csrs.htmlUntitled :: RISC-V Ratified Specifications Library
https://docs.riscv.org/reference/isa/priv/machine.htmlWeakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 13× in last 7d / 42× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
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