CVE-2026-31482

Description

In the Linux kernel, the following vulnerability has been resolved: s390/entry: Scrub r12 register on kernel entry Before commit f33f2d4c7c80 ("s390/bp: remove TIF_ISOLATE_BP"), all entry handlers loaded r12 with the current task pointer (lg %r12,__LC_CURRENT) for use by the BPENTER/BPEXIT macros. That commit removed TIF_ISOLATE_BP, dropping both the branch prediction macros and the r12 load, but did not add r12 to the register clearing sequence. Add the missing xgr %r12,%r12 to make the register scrub consistent across all entry points.

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:6.4:-:*:*:*:*:*:* - VULNERABLE

Linux Kernel (修复补丁前)

PoC / Exploit Code

⚠ For Security Research Only

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

python

// PoC for CVE-2026-31482: Check r12 register value after syscall
// Compile with: gcc -o poc_r12 poc_r12.c
// Target: s390 Architecture

#include <stdio.h>
#include <unistd.h>
#include <sys/syscall.h>

int main() {
    unsigned long r12_value;
    printf("[*] Checking r12 register content after syscall...\n");

    // Perform a syscall to trigger kernel entry
    getpid();

    // Inline assembly to read r12 (specific to s390 architecture)
    asm volatile (
        "lgr %0, 12" // Load r12 into output operand
        : "=r" (r12_value)
    );

    printf("[+] r12 value: 0x%lx\n", r12_value);
    // If r12 is not zero, it might contain leaked data
    if (r12_value != 0) {
        printf("[!] Potential data leakage detected in r12!\n");
    } else {
        printf("[+] r12 is zero (scrubbed).\n");
    }
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31482
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31482
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31482/
[4] VulDB https://vuldb.com/cve/CVE-2026-31482
[5] https://git.kernel.org/stable/c/0738d395aab8fae3b5a3ad3fc640630c91693c27
[6] https://git.kernel.org/stable/c/7f4e3233faa8470dd0627bc49b2809f2bfebd909
[7] https://git.kernel.org/stable/c/95c899cd791803a5bf7b73e5994fbbe1cc1a9c36
[8] https://git.kernel.org/stable/c/99a8b420f3f0e162eb9c9c9253929d4d23f9bd30
[9] https://git.kernel.org/stable/c/a58d298a83a3a9b7ca99ded9d60a1e77231159ef

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31482", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-22T14:16:45.457", "lastModified": "2026-04-28T13:46:21.463", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ns390/entry: Scrub r12 register on kernel entry\n\nBefore commit f33f2d4c7c80 (\"s390/bp: remove TIF_ISOLATE_BP\"),\nall entry handlers loaded r12 with the current task pointer\n(lg %r12,__LC_CURRENT) for use by the BPENTER/BPEXIT macros. That\ncommit removed TIF_ISOLATE_BP, dropping both the branch prediction\nmacros and the r12 load, but did not add r12 to the register clearing\nsequence.\n\nAdd the missing xgr %r12,%r12 to make the register scrub consistent\nacross all entry points."}], "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": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.4.1", "versionEndExcluding": "6.6.131", "matchCriteriaId": "523F816F-7981-495C-95C0-E3588239D4B9"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.80", "matchCriteriaId": "97EB19EC-A11E-49C6-9D2F-6F6EC6CB98B6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.21", "matchCriteriaId": "ED39847A-3B46-4729-B7CA-B2C30B9FA8FE"}, {"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:6.4:-:*:*:*:*:*:*", "matchCriteriaId": "DE0B0BF6-0EEF-4FAD-927D-7A0DD77BEE75"}, {"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/0738d395aab8fae3b5a3ad3fc640630c91693c27", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/7f4e3233faa8470dd0627bc49b2809f2bfebd909", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/95c899cd791803a5bf7b73e5994fbbe1cc1a9c36", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/99a8b420f3f0e162eb9c9c9253929d4d23f9bd30", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/a58d298a83a3a9b7ca99ded9d60a1e77231159ef", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}