CVE-2026-89796: Linux Vulnerability

Description

In the Linux kernel, the following vulnerability has been resolved: mm/damon/core: avoid infinite kdamond_merge_regions() internal loop Patch series "mm/damon: unurgent fixes for infinite loop, NULL de-ref and races", v1.1. Sashiko found a few issues in DAMON that could cause infinite loop, NULL dereference and monitoring results degradation. The first two sounds scary but the infinite loop happens only under unreasonable user setup. The NULL dereference is only in a unit test. Monitoring results degradation is trivial since it is only best-effort, and those happens from only unlikely races. Still those are bugs that better to fix if possible. Fix those. This patch (of 6): Due to online parameter update like events, the number of DAMON regions could be higher than the user-set upper limit. kdamond_merge_regions() repeats merge regions until the number meets the limit, while doubling the merge threshold up to the theoretical maximum threshold. It is tried only up to the theoretical maximum threshold because even the aggressive merging can fail from reducing the number of regions under the user-defined upper limit. For example, there could be many user-defined non-contiguous regions that cannot be merged. The threshold based loop break condition is evaluated by comparing the threshold for the next merging try against the theoretical maximum threshold. If max_thres is larger than UINT_MAX / 2, doubling the threshold could make it overflow, and bypass the loop break condition. In the case, if the number of regions cannot be reduced under the upper limit like explained above, the loop will run infinitely. Prevent the case by doing the break condition check before doubling the threshold. Also, prevent the threshold exceeding the maximum threshold, as it could overflow and apply the wrong merge threshold. This issue is unlikely to occur in real world, since having the max_thres higher than UINT_MAX / 2 require unrealistically large aggregation intervals compared to the sampling interval. Also, it requires an unrealistically large number of uncontiguous regions setup. Nonetheless, the consequence is bad and the fix is simple. The issue was discovered [1] by Sashiko.

Metrics

EPSS Probability

0.20%

10.6th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 310d6c15e9104c99d5d9d0ff8e5383a79da7d5e6, < 769c16699c89811386eb003c8fd9dcb8d405b316; >= 310d6c15e9104c99d5d9d0ff8e5383a79da7d5e6, < 50a7a5aec1aa43efc297fd4377c1cbdc7d15620d; >= 310d6c15e9104c99d5d9d0ff8e5383a79da7d5e6, < 8a96a06e04d210845be5d9581c0e9e338947e8f8; >= 310d6c15e9104c99d5d9d0ff8e5383a79da7d5e6, < 123e4619ab6c8ab1c4cb1d7a58311a2af13929cd; 1e865019cef354a5f0314491b4b4fc9f9a613642; d7eda72e59bbf3ed592db7ff0fd8c246c73149a8; 11078e2d11465518a9e85096bd28f8cd5fa1ea41; f2bd3184b6aeca6a497394b558337246e09fc02d; >= 5.15.164, < 5.16; >= 6.1.101, < 6.2; >= 6.6.41, < 6.7; >= 6.9.10, < 6.10
Linux	Linux	6.10

References

Timeline

Published: Sep 16, 2026
Last Modified: Sep 21, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-89796?

In the Linux kernel, the following vulnerability has been resolved: mm/damon/core: avoid infinite kdamond_merge_regions() internal loop Patch series "mm/damon: unurgent fixes for infinite loop, NULL de-ref and races", v1.1. Sashiko found a few issues in DAMON that could cause infinite loop, NULL dereference and monitoring results degradation. The first two sounds scary but the infinite loop happens only under unreasonable user setup. The NULL dereference is only in a unit test. Monitoring results degradation is trivial since it is only best-effort, and those happens from only unlikely races. Still those are bugs that better to fix if possible. Fix those. This patch (of 6): Due to online parameter update like events, the number of DAMON regions could be higher than the user-set upper limit. kdamond_merge_regions() repeats merge regions until the number meets the limit, while doubling the merge threshold up to the theoretical maximum threshold. It is tried only up to the theoretical maximum threshold because even the aggressive merging can fail from reducing the number of regions under the user-defined upper limit. For example, there could be many user-defined non-contiguous regions that cannot be merged. The threshold based loop break condition is evaluated by comparing the threshold for the next merging try against the theoretical maximum threshold. If max_thres is larger than UINT_MAX / 2, doubling the threshold could make it overflow, and bypass the loop break condition. In the case, if the number of regions cannot be reduced under the upper limit like explained above, the loop will run infinitely. Prevent the case by doing the break condition check before doubling the threshold. Also, prevent the threshold exceeding the maximum threshold, as it could overflow and apply the wrong merge threshold. This issue is unlikely to occur in real world, since having the max_thres higher than UINT_MAX / 2 require unrealistically large aggregation intervals compared to the sampling interval. Also, it requires an unrealistically large number of uncontiguous regions setup. Nonetheless, the consequence is bad and the fix is simple. The issue was discovered [1] by Sashiko.

How severe is CVE-2026-89796?

Severity scoring for CVE-2026-89796 is pending analysis. The EPSS model estimates a 0.20% probability of exploitation in the next 30 days.

How do I fix CVE-2026-89796?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

How Strix Helps

Related CVEs from 2026

View all 2026CVEs →