CVE-2026-43238
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Divide-by-Zero in Linux Kernel net/sched act_skbedit

Publication date: 2026-05-06

Last updated on: 2026-05-06

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: act_skbedit: fix divide-by-zero in tcf_skbedit_hash() Commit 38a6f0865796 ("net: sched: support hash selecting tx queue") added SKBEDIT_F_TXQ_SKBHASH support. The inclusive range size is computed as: mapping_mod = queue_mapping_max - queue_mapping + 1; The range size can be 65536 when the requested range covers all possible u16 queue IDs (e.g. queue_mapping=0 and queue_mapping_max=U16_MAX). That value cannot be represented in a u16 and previously wrapped to 0, so tcf_skbedit_hash() could trigger a divide-by-zero: queue_mapping += skb_get_hash(skb) % params->mapping_mod; Compute mapping_mod in a wider type and reject ranges larger than U16_MAX to prevent params->mapping_mod from becoming 0 and avoid the crash.
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Meta Information
Published
2026-05-06
Last Modified
2026-05-06
Generated
2026-06-16
AI Q&A
2026-05-06
EPSS Evaluated
2026-06-15
NVD
CVE-2026-43238
EUVD
EUVD-2026-27801
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
linux linux_kernel to U16_MAX (exc)
linux linux_kernel *
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
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Executive Summary

This vulnerability exists in the Linux kernel's network scheduler component, specifically in the act_skbedit module. It involves a divide-by-zero error in the function tcf_skbedit_hash().

The issue arises because the calculation of a range size (mapping_mod) for queue mappings can overflow a 16-bit unsigned integer (u16). When the range covers all possible 16-bit queue IDs, the computed size wraps around to zero instead of representing 65536. This zero value is then used as a divisor, causing a divide-by-zero error and potentially crashing the kernel.

The fix involves computing the range size in a wider data type and rejecting ranges larger than the maximum 16-bit value to prevent the zero divisor and avoid the crash.

Impact Analysis

This vulnerability can cause the Linux kernel to crash due to a divide-by-zero error in the network scheduler. Such a crash can lead to a denial of service (DoS) condition, disrupting network traffic handling and potentially affecting system stability and availability.

Mitigation Strategies

The vulnerability in the Linux kernel related to a divide-by-zero error in tcf_skbedit_hash() has been fixed by computing the mapping_mod in a wider type and rejecting ranges larger than U16_MAX to prevent the crash.

To mitigate this vulnerability, you should update your Linux kernel to a version that includes the fix for this issue, specifically the commit identified as 38a6f0865796.

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