CVE-2026-31525

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix undefined behavior in interpreter sdiv/smod for INT_MIN The BPF interpreter's signed 32-bit division and modulo handlers use the kernel abs() macro on s32 operands. The abs() macro documentation (include/linux/math.h) explicitly states the result is undefined when the input is the type minimum. When DST contains S32_MIN (0x80000000), abs((s32)DST) triggers undefined behavior and returns S32_MIN unchanged on arm64/x86. This value is then sign-extended to u64 as 0xFFFFFFFF80000000, causing do_div() to compute the wrong result. The verifier's abstract interpretation (scalar32_min_max_sdiv) computes the mathematically correct result for range tracking, creating a verifier/interpreter mismatch that can be exploited for out-of-bounds map value access. Introduce abs_s32() which handles S32_MIN correctly by casting to u32 before negating, avoiding signed overflow entirely. Replace all 8 abs((s32)...) call sites in the interpreter's sdiv32/smod32 handlers. s32 is the only affected case -- the s64 division/modulo handlers do not use abs().

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:7.0:rc1:*:*:*:*:*:* - VULNERABLE

Linux Kernel (主分支及稳定分支，具体请参考Git提交修复记录)

PoC / Exploit Code

⚠ For Security Research Only

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

python

// PoC Concept for CVE-2026-31525
// This eBPF snippet demonstrates the trigger condition.
// It attempts to perform signed division with INT_MIN.

#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>

SEC("socket")
int trigger_sdiv_min(struct __sk_buff *skb)
{
    // S32_MIN value (0x80000000)
    int s32_min = -2147483648;
    
    // The interpreter mishandles abs(s32_min) during division.
    // Verifier might track this differently than the interpreter executes.
    // Exploiting this requires complex map value manipulation.
    volatile int result = s32_min / -1;
    
    return result;
}

char _license[] SEC("license") = "GPL";

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31525
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31525
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31525/
[4] VulDB https://vuldb.com/cve/CVE-2026-31525
[5] https://git.kernel.org/stable/c/0d5d8c3ce45c734aaf3c51cbef59155a6746157d
[6] https://git.kernel.org/stable/c/694ea55f1b1c74f9942d91ec366ae9e822422e42
[7] https://git.kernel.org/stable/c/9ab1227765c446942f290c83382f0b19887c55cf
[8] https://git.kernel.org/stable/c/c77b30bd1dcb61f66c640ff7d2757816210c7cb0
[9] https://git.kernel.org/stable/c/f14ca604c0ff274fba19f73f1f0485c0047c1396

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31525", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-22T14:16:52.607", "lastModified": "2026-04-28T18:06:24.583", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix undefined behavior in interpreter sdiv/smod for INT_MIN\n\nThe BPF interpreter's signed 32-bit division and modulo handlers use\nthe kernel abs() macro on s32 operands. The abs() macro documentation\n(include/linux/math.h) explicitly states the result is undefined when\nthe input is the type minimum. When DST contains S32_MIN (0x80000000),\nabs((s32)DST) triggers undefined behavior and returns S32_MIN unchanged\non arm64/x86. This value is then sign-extended to u64 as\n0xFFFFFFFF80000000, causing do_div() to compute the wrong result.\n\nThe verifier's abstract interpretation (scalar32_min_max_sdiv) computes\nthe mathematically correct result for range tracking, creating a\nverifier/interpreter mismatch that can be exploited for out-of-bounds\nmap value access.\n\nIntroduce abs_s32() which handles S32_MIN correctly by casting to u32\nbefore negating, avoiding signed overflow entirely. Replace all 8\nabs((s32)...) call sites in the interpreter's sdiv32/smod32 handlers.\n\ns32 is the only affected case -- the s64 division/modulo handlers do\nnot use abs()."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "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-787"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "6.6.131", "matchCriteriaId": "2DC0D2CD-6CF8-469A-B3F5-E48375FDA274"}, {"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: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"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/0d5d8c3ce45c734aaf3c51cbef59155a6746157d", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/694ea55f1b1c74f9942d91ec366ae9e822422e42", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/9ab1227765c446942f290c83382f0b19887c55cf", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c77b30bd1dcb61f66c640ff7d2757816210c7cb0", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/f14ca604c0ff274fba19f73f1f0485c0047c1396", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}