CVE-2026-23440

Description

In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: Fix race condition during IPSec ESN update In IPSec full offload mode, the device reports an ESN (Extended Sequence Number) wrap event to the driver. The driver validates this event by querying the IPSec ASO and checking that the esn_event_arm field is 0x0, which indicates an event has occurred. After handling the event, the driver must re-arm the context by setting esn_event_arm back to 0x1. A race condition exists in this handling path. After validating the event, the driver calls mlx5_accel_esp_modify_xfrm() to update the kernel's xfrm state. This function temporarily releases and re-acquires the xfrm state lock. So, need to acknowledge the event first by setting esn_event_arm to 0x1. This prevents the driver from reprocessing the same ESN update if the hardware sends events for other reason. Since the next ESN update only occurs after nearly 2^31 packets are received, there's no risk of missing an update, as it will happen long after this handling has finished. Processing the event twice causes the ESN high-order bits (esn_msb) to be incremented incorrectly. The driver then programs the hardware with this invalid ESN state, which leads to anti-replay failures and a complete halt of IPSec traffic. Fix this by re-arming the ESN event immediately after it is validated, before calling mlx5_accel_esp_modify_xfrm(). This ensures that any spurious, duplicate events are correctly ignored, closing the race window.

CVSS Details

CVSS Score

7.5

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

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

cpe:2.3:o:linux:linux_kernel:6.4:-:*:*:*:*:*:* - VULNERABLE

Linux Kernel (修复补丁应用前的版本)

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * Conceptual Proof of Concept (PoC) for CVE-2026-23440
 * This PoC demonstrates the race condition logic.
 * Note: Exploiting this requires a specific environment (Linux kernel with vulnerable mlx5e driver,
 * Mellanox NIC, and IPSec offload configured). Triggering the race condition remotely involves
 * sending a high volume of traffic to trigger the ESN wrap and precise timing.
 *
 * The following Python code simulates the vulnerable logic flow.
 */

import threading
import time

class VulnerableDriver:
    def __init__(self):
        self.esn_event_arm = 0x0  # Event signaled
        self.esn_msb = 0
        self.lock = threading.Lock()
        self.xfrm_state_locked = False

    def handle_esn_event_vulnerable(self):
        print("[Driver] ESN Event Detected")
        
        # 1. Validate Event
        if self.esn_event_arm == 0x0:
            print("[Driver] Event validated.")
            
            # 2. Vulnerability: Not re-arming (setting esn_event_arm to 0x1) here.
            # We proceed to modify xfrm state which releases the lock.
            print("[Driver] Updating xfrm state (releasing lock)...")
            self.modify_xfrm_state()
            
            # 3. Re-arm happens AFTER the lock is re-acquired.
            # Race window exists between step 2 and 3.
            self.esn_event_arm = 0x1
            print("[Driver] Event re-armed.")

    def handle_esn_event_fixed(self):
        print("[Driver-Fixed] ESN Event Detected")
        
        # 1. Validate Event
        if self.esn_event_arm == 0x0:
            print("[Driver-Fixed] Event validated.")
            
            # 2. Fix: Re-arm IMMEDIATELY after validation.
            self.esn_event_arm = 0x1
            print("[Driver-Fixed] Event re-armed immediately.")
            
            # 3. Now update xfrm state
            print("[Driver-Fixed] Updating xfrm state (releasing lock)...")
            self.modify_xfrm_state()

    def modify_xfrm_state(self):
        # Simulate releasing and re-acquiring lock
        with self.lock:
            self.xfrm_state_locked = True
            time.sleep(0.1) # Simulate work
            self.xfrm_state_locked = False
        
        # Simulate hardware sending a spurious event while we are processing
        # or the logic loop checking again quickly.
        print("[Hardware] Spurious event check...")
        if self.esn_event_arm == 0x0:
            print("[Hardware] Processing event again! (BUG)")
            self.esn_msb += 1 # Incorrect increment
            print(f"[Hardware] ESN MSB incremented to {self.esn_msb}")
        else:
            print("[Hardware] Event ignored (Armed).")

# Simulation of the issue
if __name__ == "__main__":
    print("--- Simulating Vulnerable Scenario ---")
    driver = VulnerableDriver()
    driver.handle_esn_event_vulnerable() 
    # In a real race, an interrupt might trigger the check path again during modify_xfrm_state
    
    print("\n--- Simulating Fixed Scenario ---")
    driver_fixed = VulnerableDriver()
    driver_fixed.handle_esn_event_fixed()

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-23440
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-23440
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-23440/
[4] VulDB https://vuldb.com/cve/CVE-2026-23440
[5] https://git.kernel.org/stable/c/2051c709dce92da3550040aa7949cd5a9c89b14e
[6] https://git.kernel.org/stable/c/3dffc083292e6872787bd7e34b957627622f9af4
[7] https://git.kernel.org/stable/c/8d625c15471fb8780125eaef682983a96af77bdc
[8] https://git.kernel.org/stable/c/96c9c25b74686ac2de15921c9ad30c5ef13af8cd
[9] https://git.kernel.org/stable/c/beb6e2e5976a128b0cccf10d158124422210c5ef

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-23440", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-03T16:16:26.020", "lastModified": "2026-04-27T14:16:32.883", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/mlx5e: Fix race condition during IPSec ESN update\n\nIn IPSec full offload mode, the device reports an ESN (Extended\nSequence Number) wrap event to the driver. The driver validates this\nevent by querying the IPSec ASO and checking that the esn_event_arm\nfield is 0x0, which indicates an event has occurred. After handling\nthe event, the driver must re-arm the context by setting esn_event_arm\nback to 0x1.\n\nA race condition exists in this handling path. After validating the\nevent, the driver calls mlx5_accel_esp_modify_xfrm() to update the\nkernel's xfrm state. This function temporarily releases and\nre-acquires the xfrm state lock.\n\nSo, need to acknowledge the event first by setting esn_event_arm to\n0x1. This prevents the driver from reprocessing the same ESN update if\nthe hardware sends events for other reason. Since the next ESN update\nonly occurs after nearly 2^31 packets are received, there's no risk of\nmissing an update, as it will happen long after this handling has\nfinished.\n\nProcessing the event twice causes the ESN high-order bits (esn_msb) to\nbe incremented incorrectly. The driver then programs the hardware with\nthis invalid ESN state, which leads to anti-replay failures and a\ncomplete halt of IPSec traffic.\n\nFix this by re-arming the ESN event immediately after it is validated,\nbefore calling mlx5_accel_esp_modify_xfrm(). This ensures that any\nspurious, duplicate events are correctly ignored, closing the race\nwindow."}], "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:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 4.7, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.0, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-362"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.4.1", "versionEndExcluding": "6.6.130", "matchCriteriaId": "5ED2C179-5F1F-4BB1-9DEA-A21F23BC569B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.78", "matchCriteriaId": "28D591F5-B196-4CC9-905C-DC80F116E7A8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.20", "matchCriteriaId": "E5571059-6552-48E7-9BEF-3E358C387171"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.10", "matchCriteriaId": "96D34333-38BE-4414-9E79-6EB764329581"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.4:-:*:*:*:*:*:*", "matchCriteriaId": "DE0B0BF6-0EEF-4FAD-927D-7A0DD77BEE75"}, {"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"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*", "matchCriteriaId": "512EE3A8-A590-4501-9A94-5D4B268D6138"}]}]}], "references": [{"url": "http ... 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