# CVE-2023-53699: riscv: move memblock_allow_resize() after linear mapping is ready

> A flaw in the Linux kernel RISC-V architecture allows a page fault during early boot, potentially causing a denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Not stated
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Oct 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2023-53699, DEBIAN-CVE-2023-53699, GHSA-q328-fmmj-x9cj, ROOT-OS-DEBIAN-11-CVE-2023-53699, UBUNTU-CVE-2023-53699

## What is CVE-2023-53699?

CVE-2023-53699 is a vulnerability in Linux, published on 22 Oct 2025. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

riscv: move memblock_allow_resize() after linear mapping is ready

The initial memblock metadata is accessed from kernel image mapping. The
regions arrays need to "reallocated" from memblock and accessed through
linear mapping to cover more memblock regions. So the resizing should
not be allowed until linear mapping is ready. Note that there are
memblock allocations when building linear mapping.

This patch is similar to 24cc61d8cb5a ("arm64: memblock: don't permit
memblock resizing until linear mapping is up").

In following log, many memblock regions are reserved before
create_linear_mapping_page_table(). And then it triggered reallocation
of memblock.reserved.regions and memcpy the old array in kernel image
mapping to the new array in linear mapping which caused a page fault.

[    0.000000] memblock_reserve: [0x00000000bf01f000-0x00000000bf01ffff] early_init_fdt_scan_reserved_mem+0x28c/0x2c6
[    0.000000] memblock_reserve: [0x00000000bf021000-0x00000000bf021fff] early_init_fdt_scan_reserved_mem+0x28c/0x2c6
[    0.000000] memblock_reserve: [0x00000000bf023000-0x00000000bf023fff] early_init_fdt_scan_reserved_mem+0x28c/0x2c6
[    0.000000] memblock_reserve: [0x00000000bf025000-0x00000000bf025fff] early_init_fdt_scan_reserved_mem+0x28c/0x2c6
[    0.000000] memblock_reserve: [0x00000000bf027000-0x00000000bf027fff] early_init_fdt_scan_reserved_mem+0x28c/0x2c6
[    0.000000] memblock_reserve: [0x00000000bf029000-0x00000000bf029fff] early_init_fdt_scan_reserved_mem+0x28c/0x2c6
[    0.000000] memblock_reserve: [0x00000000bf02b000-0x00000000bf02bfff] early_init_fdt_scan_reserved_mem+0x28c/0x2c6
[    0.000000] memblock_reserve: [0x00000000bf02d000-0x00000000bf02dfff] early_init_fdt_scan_reserved_mem+0x28c/0x2c6
[    0.000000] memblock_reserve: [0x00000000bf02f000-0x00000000bf02ffff] early_init_fdt_scan_reserved_mem+0x28c/0x2c6
[    0.000000] memblock_reserve: [0x00000000bf030000-0x00000000bf030fff] early_init_fdt_scan_reserved_mem+0x28c/0x2c6
[    0.000000] OF: reserved mem: 0x0000000080000000..0x000000008007ffff (512 KiB) map non-reusable mmode_resv0@80000000
[    0.000000] memblock_reserve: [0x00000000bf000000-0x00000000bf001fed] paging_init+0x19a/0x5ae
[    0.000000] memblock_phys_alloc_range: 4096 bytes align=0x1000 from=0x0000000000000000 max_addr=0x0000000000000000 alloc_pmd_fixmap+0x14/0x1c
[    0.000000] memblock_reserve: [0x000000017ffff000-0x000000017fffffff] memblock_alloc_range_nid+0xb8/0x128
[    0.000000] memblock: reserved is doubled to 256 at [0x000000017fffd000-0x000000017fffe7ff]
[    0.000000] Unable to handle kernel paging request at virtual address ff600000ffffd000
[    0.000000] Oops [#1]
[    0.000000] Modules linked in:
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 6.4.0-rc1-00011-g99a670b2069c #66
[    0.000000] Hardware name: riscv-virtio,qemu (DT)
[    0.000000] epc : __memcpy+0x60/0xf8
[    0.000000]  ra : memblock_double_array+0x192/0x248
[    0.000000] epc : ffffffff8081d214 ra : ffffffff80a3dfc0 sp : ffffffff81403bd0
[    0.000000]  gp : ffffffff814fbb38 tp : ffffffff8140dac0 t0 : 0000000001600000
[    0.000000]  t1 : 0000000000000000 t2 : 000000008f001000 s0 : ffffffff81403c60
[    0.000000]  s1 : ffffffff80c0bc98 a0 : ff600000ffffd000 a1 : ffffffff80c0bcd8
[    0.000000]  a2 : 0000000000000c00 a3 : ffffffff80c0c8d8 a4 : 0000000080000000
[    0.000000]  a5 : 0000000000080000 a6 : 0000000000000000 a7 : 0000000080200000
[    0.000000]  s2 : ff600000ffffd000 s3 : 0000000000002000 s4 : 0000000000000c00
[    0.000000]  s5 : ffffffff80c0bc60 s6 : ffffffff80c0bcc8 s7 : 0000000000000000
[    0.000000]  s8 : ffffffff814fd0a8 s9 : 000000017fffe7ff s10: 0000000000000000
[    0.000000]  s11: 0000000000001000 t3 : 0000000000001000 t4 : 0000000000000000
[    0.000000]  t5 : 000000008f003000 t6 : ff600000ffffd000
[    0.000000] status: 0000000200000100 badaddr: ff600000ffffd000 cause: 000000000000000f
[    0.000000] [<fff
---truncated---

## Which versions are affected by CVE-2023-53699?


## How do I fix CVE-2023-53699?

Apply the vendor's patch.

## Is CVE-2023-53699 being exploited?

There is no known exploitation of CVE-2023-53699 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-53699 and fix it if it is affected.

What it is: CVE-2023-53699 is a vulnerability in Linux, published on 22 Oct 2025. 
Exploitation: There is no known exploitation of CVE-2023-53699 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-53699/ (Markdown: https://insights.sbomify.com/CVE-2023-53699/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-53699
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-53699
- OSV: https://osv.dev/vulnerability/CVE-2023-53699

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-53699/
Summaries are generated and may contain mistakes; the official description above is the record.