CVE-2026-23455

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() In DecodeQ931(), the UserUserIE code path reads a 16-bit length from the packet, then decrements it by 1 to skip the protocol discriminator byte before passing it to DecodeH323_UserInformation(). If the encoded length is 0, the decrement wraps to -1, which is then passed as a large value to the decoder, leading to an out-of-bounds read. Add a check to ensure len is positive after the decrement.

CVSS Details

CVSS Score

9.1

Severity

CRITICAL

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

Linux Kernel < 6.6 (具体受影响版本请参考Git补丁提交记录)

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * PoC Concept for CVE-2026-23455
 * This C code demonstrates the logic error in DecodeQ931.
 * It simulates the integer underflow when length is 0.
 */

#include <stdio.h>
#include <stdint.h>

// Simulated vulnerable function logic
void vulnerable_decode_q931(uint16_t ie_len) {
    printf("[VULN] Initial IE Length: %u\n", ie_len);
    
    // The vulnerable operation: decrement without checking for 0
    ie_len--; 
    
    printf("[VULN] Length after decrement: %u\n", ie_len);
    
    if (ie_len > 1024) {
        printf("[EXPLOIT] Potential Out-of-Bounds Read detected! Length is too large.\n");
    }
}

// Simulated patched function logic
void patched_decode_q931(uint16_t ie_len) {
    printf("[PATCH] Initial IE Length: %u\n", ie_len);
    
    // Patch: Check for underflow before decrementing
    if (ie_len == 0) {
        printf("[PATCH] Invalid length 0, aborting.\n");
        return;
    }
    
    ie_len--;
    printf("[PATCH] Length after decrement: %u\n", ie_len);
}

int main() {
    printf("--- Testing Vulnerable Logic ---\n");
    // Malicious packet with length 0
    vulnerable_decode_q931(0);
    
    printf("\n--- Testing Patched Logic ---\n");
    patched_decode_q931(0);
    
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-23455
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-23455
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-23455/
[4] VulDB https://vuldb.com/cve/CVE-2026-23455
[5] https://git.kernel.org/stable/c/2121f5fbe88daff0f1fc5bc47d359426c74b86b0
[6] https://git.kernel.org/stable/c/495e97af9e7249ee02b72bb1d0848a6efc3700f4
[7] https://git.kernel.org/stable/c/633e8f87dad32263f6a57dccdb873f042c062111
[8] https://git.kernel.org/stable/c/65fa92f79677858b14b9e4b7275f26639afe2710
[9] https://git.kernel.org/stable/c/9d00fe7d6d7c5b5f1065a6e042b54f2e44bd6df8
[10] https://git.kernel.org/stable/c/b652b05d51003ac074b912684f9ec7486231717b
[11] https://git.kernel.org/stable/c/f173d0f4c0f689173f8cdac79991043a4a89bf66
[12] https://git.kernel.org/stable/c/f5e4f4e4cdb75ec36802059a94195a31f193da60

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-23455", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-03T16:16:32.123", "lastModified": "2026-04-27T14:16:33.940", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_h323: check for zero length in DecodeQ931()\n\nIn DecodeQ931(), the UserUserIE code path reads a 16-bit length from\nthe packet, then decrements it by 1 to skip the protocol discriminator\nbyte before passing it to DecodeH323_UserInformation(). If the encoded\nlength is 0, the decrement wraps to -1, which is then passed as a\nlarge value to the decoder, leading to an out-of-bounds read.\n\nAdd a check to ensure len is positive after the decrement."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H", "baseScore": 9.1, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.2}]}, "references": [{"url": "https://git.kernel.org/stable/c/2121f5fbe88daff0f1fc5bc47d359426c74b86b0", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/495e97af9e7249ee02b72bb1d0848a6efc3700f4", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/633e8f87dad32263f6a57dccdb873f042c062111", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/65fa92f79677858b14b9e4b7275f26639afe2710", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/9d00fe7d6d7c5b5f1065a6e042b54f2e44bd6df8", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/b652b05d51003ac074b912684f9ec7486231717b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/f173d0f4c0f689173f8cdac79991043a4a89bf66", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/f5e4f4e4cdb75ec36802059a94195a31f193da60", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}]}}