CVE-2026-45254

Description

In the case of the cap_net service, when a key present in the old limit was omitted from the new limit, the missing key was treated as "allow any" instead of being rejected. In certain scenarios, an application that had previously restricted a subset of network operations could ask for a new limit that extended the permissions of the process.

CVSS Details

CVSS Score

6.5

Severity

MEDIUM

CVSS Vector

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

Configurations (Affected Products)

cpe:2.3:o:freebsd:freebsd:14.3:-:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:freebsd:freebsd:14.3:p1:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:freebsd:freebsd:14.3:p10:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:freebsd:freebsd:14.3:p11:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:freebsd:freebsd:14.3:p12:*:*:*:*:*:* - VULNERABLE

FreeBSD (受限于FreeBSD-SA-26:24影响)

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * PoC for CVE-2026-45254: FreeBSD cap_net Logic Flaw
 * This code demonstrates the concept where omitting a key in the new limit
 * results in "allow any" instead of rejection.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// Hypothetical structure for cap_net limits
struct cap_limit {
    char key[64];
    int action; // 0: deny, 1: allow
};

// Simulated vulnerable function to update limits
void update_limits_vulnerable(struct cap_limit *old_limits, int old_count, struct cap_limit *new_limits, int new_count) {
    printf("[VULNERABLE] Updating limits...\n");
    
    // In the vulnerable scenario, the system assumes missing keys are implicitly allowed
    for (int i = 0; i < old_count; i++) {
        int found = 0;
        for (int j = 0; j < new_count; j++) {
            if (strcmp(old_limits[i].key, new_limits[j].key) == 0) {
                found = 1;
                break;
            }
        }
        
        if (!found) {
            printf("Key '%s' omitted in new limits. Treating as ALLOW ANY (VULNERABILITY)!\n", old_limits[i].key);
        }
    }
}

int main() {
    // Initial strict limits: restrict HTTP and DNS
    struct cap_limit old_limits[2];
    strcpy(old_limits[0].key, "net.http");
    old_limits[0].action = 0; // Deny
    strcpy(old_limits[1].key, "net.dns");
    old_limits[1].action = 0; // Deny

    // New limits: Only explicitly restrict HTTP, omitting DNS
    struct cap_limit new_limits[1];
    strcpy(new_limits[0].key, "net.http");
    new_limits[0].action = 0; // Deny

    // Trigger the vulnerable logic
    update_limits_vulnerable(old_limits, 2, new_limits, 1);

    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-45254
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-45254
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-45254/
[4] VulDB https://vuldb.com/cve/CVE-2026-45254
[5] https://security.freebsd.org/advisories/FreeBSD-SA-26:24.cap_net.asc

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-45254", "sourceIdentifier": "[email protected]", "published": "2026-05-21T10:16:26.380", "lastModified": "2026-05-21T19:00:47.593", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the case of the cap_net service, when a key present in the old limit was omitted from the new limit, the missing key was treated as \"allow any\" instead of being rejected.\n\nIn certain scenarios, an application that had previously restricted a subset of network operations could ask for a new limit that extended the permissions of the process."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N", "baseScore": 6.5, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 2.5}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-269"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:-:*:*:*:*:*:*", "matchCriteriaId": "9DC7C54E-58AF-4ADE-84AF-0EF0F325E20E"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p1:*:*:*:*:*:*", "matchCriteriaId": "D3D22B8C-36CF-4800-9673-0B0240558BDD"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p10:*:*:*:*:*:*", "matchCriteriaId": "7296F5AA-F8C1-4277-A4EE-C2B24073A320"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p11:*:*:*:*:*:*", "matchCriteriaId": "C30E4A9C-0594-4F40-92B3-26CB9AA85AE9"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p12:*:*:*:*:*:*", "matchCriteriaId": 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