# CVE-2025-38723: LoongArch: BPF: Fix jump offset calculation in tailcall

> A bug in the Linux kernel's LoongArch BPF JIT compiler causes incorrect jump offsets, leading to CPU soft lockups and denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Sep 2025
- **Updated:** 12 May 2026
- **Also known as:** AZL-66791, BELL-CVE-2025-38723, DEBIAN-CVE-2025-38723, GHSA-wvjq-jmp5-gvcr, ROOT-OS-DEBIAN-12-CVE-2025-38723, ROOT-OS-UBUNTU-2404-CVE-2025-38723, UBUNTU-CVE-2025-38723

## What is CVE-2025-38723?

CVE-2025-38723 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 4 Sep 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

LoongArch: BPF: Fix jump offset calculation in tailcall

The extra pass of bpf_int_jit_compile() skips JIT context initialization
which essentially skips offset calculation leaving out_offset = -1, so
the jmp_offset in emit_bpf_tail_call is calculated by

"#define jmp_offset (out_offset - (cur_offset))"

is a negative number, which is wrong. The final generated assembly are
as follow.

54:	bgeu        	$a2, $t1, -8	    # 0x0000004c
58:	addi.d      	$a6, $s5, -1
5c:	bltz        	$a6, -16	    # 0x0000004c
60:	alsl.d      	$t2, $a2, $a1, 0x3
64:	ld.d        	$t2, $t2, 264
68:	beq         	$t2, $zero, -28	    # 0x0000004c

Before apply this patch, the follow test case will reveal soft lock issues.

cd tools/testing/selftests/bpf/
./test_progs --allow=tailcalls/tailcall_bpf2bpf_1

dmesg:
watchdog: BUG: soft lockup - CPU#2 stuck for 26s! [test_progs:25056]

## Which versions are affected by CVE-2025-38723?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-38723?

Apply the vendor's patch.

## Is CVE-2025-38723 being exploited?

There is no known exploitation of CVE-2025-38723 in the wild and no public exploit code.

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- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-38723 and fix it if it is affected.

What it is: CVE-2025-38723 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 4 Sep 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-38723 in the wild and no public exploit code.

Affected product: Debian Debian 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-2025-38723/ (Markdown: https://insights.sbomify.com/CVE-2025-38723/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38723
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38723
- OSV: https://osv.dev/vulnerability/CVE-2025-38723

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38723/
Summaries are generated and may contain mistakes; the official description above is the record.