CVE-2026-99018riscv: entry: gate shadow call stack reload on sstatus.SPP, not tp
- 7.8HighCVSS base score
- 0.18%Exploitation in 30 daysEPSS · top 93% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In the Linux kernel, the following vulnerability has been resolved: riscv: entry: gate shadow call stack reload on sstatus.SPP, not tp Under CONFIG_SHADOW_CALL_STACK, handle_exception() reloads the kernel shadow call stack pointer (gp) only when the trap came from userspace. It made that decision with scs_load_current_if_task_changed, which compares the trap-time tp (read back from sscratch into s5) against the current tp: beq \prev, tp, _skip_scs scs_load_current _skip_scs: tp is a user-writable register. A user task that sets tp to the linear-map address of its own task_struct (¤t) before trapping makes the comparison succeed (can achieve by brute force with KASLR enable under our test), so the kernel skips scs_load_current and keeps running with the gp that userspace left in place. Under CONFIG_SHADOW_CALL_STACK gp is the shadow call stack pointer and load_global_pointer is a no-op, so the compiler-emitted "sd ra, -8(gp)" / "ld ra, -8(gp)" in every non-leaf function then write to, and return through, an attacker-controlled address -- an unprivileged kernel arbitrary-write and control-flow-hijack primitive. The poisoned gp is saved to task_struct.scs_sp on return, so the reload is skipped on every subsequent entry as well. Decide "came from userspace" from the hardware sstatus.SPP bit (already in s1 at this point) instead of from tp, mirroring the check that ret_from_exception already uses a few instructions later. SPP is written by hardware on trap entry and cannot be forged from U-mode. Legitimate behaviour is unchanged: user entries (SPP=0) reload the task shadow call stack, nested kernel entries (SPP=1) skip it.
Timeline
ID reserved
By Linux
- 28 days later
· 28 days later
Published
- 1 day later
· 1 day later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Received | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.18% · top 93% of all CVEs (14 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.
Affected products
- affected d1584d791a297aa8ed93503382a682a6ecfc4218 – < 6639735367a7d491977e9e5e7afc50b489d81d83
- affected d1584d791a297aa8ed93503382a682a6ecfc4218 – < 7d1367a53137e379498eb8791295e58854378636
- affected d1584d791a297aa8ed93503382a682a6ecfc4218 – < 37b4401ee6fa06046446d55e97e8d11784080843
- affected d1584d791a297aa8ed93503382a682a6ecfc4218 – < 4d0697f192975dab5985e921989be1d85cf580e9
- affected 6.7
- unaffected < 6.7
- unaffected 6.12.113 – ≤ 6.12.*
- unaffected 6.18.57 – ≤ 6.18.*
- unaffected 7.2.11 – ≤ 7.2.*
- unaffected 7.3 – ≤ *
References
References4
- https://git.kernel.org/stable/c/6639735367a7d491977e9e5e7afc50b489d81d83 (opens in a new tab)
- https://git.kernel.org/stable/c/7d1367a53137e379498eb8791295e58854378636 (opens in a new tab)
- https://git.kernel.org/stable/c/37b4401ee6fa06046446d55e97e8d11784080843 (opens in a new tab)
- https://git.kernel.org/stable/c/4d0697f192975dab5985e921989be1d85cf580e9 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-108812 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-99018)Record last updated .