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VulnerabilityPublished Updated

CVE-2026-99018: Linux kernel · riscv: entry: gate shadow call stack reload on sstatus.SPP, not tp

Affects Linux kernelSource CVE Database V5

0

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

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.
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:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 23 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ d1584d791a297aa8ed93503382a682a6ecfc4218, < 6639735367a7d491977e9e5e7afc50b489d81d83
Fixed in
  • 6639735367a7d491977e9e5e7afc50b489d81d83
LinuxLinuxAffected
  • ≥ d1584d791a297aa8ed93503382a682a6ecfc4218, < 37b4401ee6fa06046446d55e97e8d11784080843
Fixed in
  • 37b4401ee6fa06046446d55e97e8d11784080843
LinuxLinuxAffected
  • ≥ d1584d791a297aa8ed93503382a682a6ecfc4218, < 7d1367a53137e379498eb8791295e58854378636
Fixed in
  • 7d1367a53137e379498eb8791295e58854378636
LinuxLinuxAffected
  • ≥ d1584d791a297aa8ed93503382a682a6ecfc4218, < 4d0697f192975dab5985e921989be1d85cf580e9
Fixed in
  • 4d0697f192975dab5985e921989be1d85cf580e9
LinuxLinuxAffected
  • =6.7
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

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