Missing Default Case in Switch Statement Affecting kernel-tools-libs-devel package, versions *


Severity

Recommended
low

Based on CentOS security rating.

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  • Snyk IDSNYK-CENTOS8-KERNELTOOLSLIBSDEVEL-12648180
  • published12 Sept 2025
  • disclosed11 Sept 2025

Introduced: 11 Sep 2025

NewCVE-2025-39748  (opens in a new tab)
CWE-478  (opens in a new tab)

How to fix?

There is no fixed version for Centos:8 kernel-tools-libs-devel.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-tools-libs-devel package and not the kernel-tools-libs-devel package as distributed by Centos. See How to fix? for Centos:8 relevant fixed versions and status.

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

bpf: Forget ranges when refining tnum after JSET

Syzbot reported a kernel warning due to a range invariant violation on the following BPF program.

0: call bpf_get_netns_cookie 1: if r0 == 0 goto <exit> 2: if r0 & Oxffffffff goto <exit>

The issue is on the path where we fall through both jumps.

That path is unreachable at runtime: after insn 1, we know r0 != 0, but with the sign extension on the jset, we would only fallthrough insn 2 if r0 == 0. Unfortunately, is_branch_taken() isn't currently able to figure this out, so the verifier walks all branches. The verifier then refines the register bounds using the second condition and we end up with inconsistent bounds on this unreachable path:

1: if r0 == 0 goto <exit> r0: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0xffffffffffffffff) 2: if r0 & 0xffffffff goto <exit> r0 before reg_bounds_sync: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0) r0 after reg_bounds_sync: u64=[0x1, 0] var_off=(0, 0)

Improving the range refinement for JSET to cover all cases is tricky. We also don't expect many users to rely on JSET given LLVM doesn't generate those instructions. So instead of improving the range refinement for JSETs, Eduard suggested we forget the ranges whenever we're narrowing tnums after a JSET. This patch implements that approach.

CVSS Base Scores

version 3.1