CVE-2026-63836 Affecting kernel-kvmsmall package, versions <6.12.0-160000.37.1


Severity

Recommended
0.0
medium
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.17% (8th percentile)

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  • Snyk IDSNYK-SLES1600-KERNELKVMSMALL-19334995
  • published27 Aug 2026
  • disclosed11 Aug 2026

Introduced: 11 Aug 2026

NewCVE-2026-63836  (opens in a new tab)

How to fix?

Upgrade SLES:16.0.0 kernel-kvmsmall to version 6.12.0-160000.37.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-kvmsmall package and not the kernel-kvmsmall package as distributed by SLES. See How to fix? for SLES:16.0.0 relevant fixed versions and status.

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

batman-adv: tp_meter: avoid divide-by-zero for dec_cwnd

The cwnd is always MSS <= cwnd <= 0x20000000. But the calculation in batadv_tp_update_cwnd() assumes unsigned 32 bit arithmetics.

((mss * 8) ** 2) / (cwnd * 8)

In case cwnd is actually 0x20000000, it will be shifted by 3 bit to the left end up at 0x100000000 or U32_MAX + 1. It will therefore wrap around and be 0 - resulting in:

((mss * 8) ** 2) / 0

This is of course invalid and cannot be calculated. The calculation should must be simplified to avoid this overflow:

(mss ** 2) * 8 / cwnd

It will keep the precision enhancement from the scaling (by 8) but avoid the overflow in the divisor.

In theory, there could still be an overflow in the dividend. It is at the moment fixed to BATADV_TP_PLEN in batadv_tp_recv_ack() - so it is not an imminent problem. But allowing it to use the whole u32 bit range, would mean that it can still use up to 67 bits. To keep this calculation safe for 32 bit arithmetic, mss must never use more than floor((32 - 3) / 2) bits - or in other words: must never be larger than 16383.

CVSS Base Scores

version 3.1