CVE-2026-99018: Linux kernel · riscv: entry: gate shadow call stack reload on sstatus.SPP, not tp
Affects Linux kernelSource CVE Database V5
Not known to be exploited · CVSS 7.8 High · fixed in 6639735367a7d491977e9e5e7afc50b489d81d83 : patch Linux kernel soon.
Data as of 26 Oct 2026, 12:42 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6639735367a7d491977e9e5e7afc50b489d81d83, 37b4401ee6fa06046446d55e97e8d11784080843, 7d1367a53137e379498eb8791295e58854378636 +1
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 23 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade Linux kernel to 6639735367a7d491977e9e5e7afc50b489d81d83, 37b4401ee6fa06046446d55e97e8d11784080843, 7d1367a53137e379498eb8791295e58854378636 or 4d0697f192975dab5985e921989be1d85cf580e9.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in– |
AI-suggested
A fix is available and has been applied in Linux kernel version 6.7 and later. Users should upgrade to version 6.7 or a later fixed release to remediate this vulnerability. No additional mitigations are required as the patch corrects the fundamental logic error in trap origin determination.
Description
CVE-2026-99018 is a high-severity vulnerability in the Linux kernel affecting the RISC-V architecture under CONFIG_SHADOW_CALL_STACK. The kernel incorrectly determines whether a trap came from userspace by comparing a user-writable register (tp) instead of using the hardware sstatus.SPP bit. This flaw allows an unprivileged user to manipulate the shadow call stack pointer, enabling arbitrary kernel memory write and control-flow hijacking. The issue is fixed by changing the check to rely on the hardware-controlled sstatus.SPP bit, which cannot be forged by user mode.
References
- git.kernel.org/stable/c/6639735367a7d491977e9e5e7afc50b489d81d83 (opens in a new tab)
- git.kernel.org/stable/c/7d1367a53137e379498eb8791295e58854378636 (opens in a new tab)
- git.kernel.org/stable/c/37b4401ee6fa06046446d55e97e8d11784080843 (opens in a new tab)
- git.kernel.org/stable/c/4d0697f192975dab5985e921989be1d85cf580e9 (opens in a new tab)