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

net/sched: sch_hfsc: fix divide-by-zero in rtsc_min()

m2sm() converts a u32 slope to a u64 scaled value. For large inputs
(e.g. m1=4000000000), the result can reach 2^32. rtsc_min() stores
the difference of two such u64 values in a u32 variable `dsm` and
uses it as a divisor. When the difference is exactly 2^32 the
truncation yields zero, causing a divide-by-zero oops in the
concave-curve intersection path:

Oops: divide error: 0000
RIP: 0010:rtsc_min (net/sched/sch_hfsc.c:601)
Call Trace:
init_ed (net/sched/sch_hfsc.c:629)
hfsc_enqueue (net/sched/sch_hfsc.c:1569)
[...]

Widen `dsm` to u64 and replace do_div() with div64_u64() so the full
difference is preserved.
Published: 2026-04-13
Score: 5.5 Medium
EPSS: < 1% Very Low
KEV: No
Impact: Denial of Service via kernel crash
Action: Apply Patch
AI Analysis

Impact

The flaw lies in the Linux kernel traffic scheduler module, where a division by zero occurs in the rtsc_min() function of the HFSC scheduler. When a particular calculation yields a divisor of zero due to integer truncation, the kernel raises an oops exception that forces a crash. This results in a denial of service, preventing the kernel or affected processes from continuing until a reboot or restart.

Affected Systems

The vulnerability is present in any Linux kernel that implements the HFSC fair scheduling algorithm. The advisory does not specify which kernel releases are affected, so all builds containing the current sch_hfsc implementation may be vulnerable until a patched release is applied.

Risk and Exploitability

The CVSS score of 5.5 indicates a moderate severity. The issue is not listed in the CISA KEV catalog and no EPSS score is available. Exploitation would require triggering the HFSC scheduler with crafted traffic, implying a local or privileged access requirement. The precise attack vector is not detailed, but an attacker that can cause the scheduler to process malicious packets can induce a kernel crash and temporary denial of service.

Generated by OpenCVE AI on April 14, 2026 at 01:27 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Apply the latest kernel update that incorporates the fix for the divide‑by‑zero issue in sch_hfsc.
  • Verify your running kernel version and upgrade to a patched release as soon as possible.

Generated by OpenCVE AI on April 14, 2026 at 01:27 UTC.

Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-4561-1 linux-6.1 security update
Debian DSA Debian DSA DSA-6238-1 linux security update
Debian DSA Debian DSA DSA-6243-1 linux security update
History

Sat, 18 Apr 2026 09:15:00 +0000


Tue, 14 Apr 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-369
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate


Mon, 13 Apr 2026 13:45:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_hfsc: fix divide-by-zero in rtsc_min() m2sm() converts a u32 slope to a u64 scaled value. For large inputs (e.g. m1=4000000000), the result can reach 2^32. rtsc_min() stores the difference of two such u64 values in a u32 variable `dsm` and uses it as a divisor. When the difference is exactly 2^32 the truncation yields zero, causing a divide-by-zero oops in the concave-curve intersection path: Oops: divide error: 0000 RIP: 0010:rtsc_min (net/sched/sch_hfsc.c:601) Call Trace: init_ed (net/sched/sch_hfsc.c:629) hfsc_enqueue (net/sched/sch_hfsc.c:1569) [...] Widen `dsm` to u64 and replace do_div() with div64_u64() so the full difference is preserved.
Title net/sched: sch_hfsc: fix divide-by-zero in rtsc_min()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-04-18T08:59:36.227Z

Reserved: 2026-03-09T15:48:24.088Z

Link: CVE-2026-31423

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-04-13T14:16:12.070

Modified: 2026-04-18T09:16:32.270

Link: CVE-2026-31423

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-04-13T00:00:00Z

Links: CVE-2026-31423 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-04-14T16:34:25Z

Weaknesses