CVE-2026-31674

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: ip6t_rt: reject oversized addrnr in rt_mt6_check() Reject rt match rules whose addrnr exceeds IP6T_RT_HOPS. rt_mt6() expects addrnr to stay within the bounds of rtinfo->addrs[]. Validate addrnr during rule installation so malformed rules are rejected before the match logic can use an out-of-range value.

CVSS Details

CVSS Score

7.1

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

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

Linux Kernel (修复前版本)

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * PoC Concept for CVE-2026-31674
 * This code demonstrates how to structure a malicious rule that bypasses
 * the buggy check in rt_mt6_check(), leading to out-of-bounds access.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <linux/netfilter_ipv6/ip6_tables.h>

// Define the maximum allowed hops (usually defined in kernel headers)
#define IP6T_RT_HOPS 3

// Simplified structure representing the vulnerable match info
struct ip6t_rt_info {
    __u32 flags;
    __u32 invflags;
    __u16 rt_type;
    __u16 segsleft[2];
    __u16 hdrlen;
    __u8  lastseg;
    __u8  addrnr; // Vulnerable field
    __u16 reserved;
    struct in6_addr addrs[1];
};

int main() {
    struct ip6t_rt_info rt_rule;
    memset(&rt_rule, 0, sizeof(rt_rule));

    // Set addrnr to a value exceeding IP6T_RT_HOPS
    // This simulates the malicious payload
    rt_rule.addrnr = 10; 

    printf("[+] Crafting malicious netfilter rule...\n");
    printf("[+] addrnr set to: %d (Max allowed: %d)\n", rt_rule.addrnr, IP6T_RT_HOPS);
    printf("[!] If loaded, rt_mt6() will access addrs[%d], causing OOB access.\n", rt_rule.addrnr);

    // In a real exploit scenario, this structure would be passed to the kernel
    // via setsockopt() using IPT_SO_SET_REPLACE.
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31674
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31674
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31674/
[4] VulDB https://vuldb.com/cve/CVE-2026-31674
[5] https://git.kernel.org/stable/c/13e3e30ed3b5b67cc1db2bd58a5d09b0f07debfa
[6] https://git.kernel.org/stable/c/29ea965a1353bc8303877422f79c8211e9ba9c55
[7] https://git.kernel.org/stable/c/9d3f027327c2fa265f7f85ead41294792c3296ed
[8] https://git.kernel.org/stable/c/a28ebf6f99de270d6338ccdc3b49f3e818f99b7b
[9] https://git.kernel.org/stable/c/af9b7e2b765966457f4ec23be5bd34a141f89574
[10] https://git.kernel.org/stable/c/c6a503a9f4debc654e3a6a7ca1f7fce6a9953c59
[11] https://git.kernel.org/stable/c/d8795fde1f78669a87c87ac29fceab2f104daa8c
[12] https://git.kernel.org/stable/c/ded71f5684df16fa645cca5bf4fe6b0cd8a46119

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31674", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-25T09:16:00.963", "lastModified": "2026-05-06T21:34:51.447", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: ip6t_rt: reject oversized addrnr in rt_mt6_check()\n\nReject rt match rules whose addrnr exceeds IP6T_RT_HOPS.\n\nrt_mt6() expects addrnr to stay within the bounds of rtinfo->addrs[].\nValidate addrnr during rule installation so malformed rules are rejected\nbefore the match logic can use an out-of-range value."}], "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:N/A:H", "baseScore": 7.1, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.2}]}, "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": "2.6.12.1", "versionEndExcluding": "5.10.253", "matchCriteriaId": "5F0E43E1-33E5-4828-9B4A-F710AF2E7217"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.203", "matchCriteriaId": "20DDB3E9-AABF-4107-ADB0-5362AA067045"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.168", "matchCriteriaId": "E2DDDCA1-6DAB-4018-B920-8F045DDD8D3B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.131", "matchCriteriaId": "CE6ED4D4-0046-4573-BFA9-D64143B6A89F"}, {"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:2.6.12:-:*:*:*:*:*:*", "matchCriteriaId": "6F62EECE-8FB1-4D57-85D8-CB9E23CF313C"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc2:*:*:*:*:*:*", "matchCriteriaId": "4F76C298-81DC-43E4-8FC9-DC005A2116EF"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc3:*:*:*:*:*:*", "matchCriteriaId": "0AB349B2-3F78-4197-882B-90ADB3BF645A"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc4:*:*:*:*:*:*", "matchCriteriaId": "6AC88830-A9BC-4607-B572-A4B502FC9FD0"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc5:*:*:*:*:*:*", "matchCriteriaId": "476CB3A5-D022-4F13-AAEF-CB6A5785516A"}, {"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/13e3e30ed3b5b67cc1db2bd58a5d09b0f07debfa", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/29ea965a1353bc8303877422f79c8211e9ba9c55", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/9d3f027327c2fa265f7f85ead41294792c3296ed", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/a28ebf6f99de270d6338ccdc3b49f3e818f99b7b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/af9b7e2b765966457f4ec23be5bd3 ... (truncated)