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CVE-2026-23240

Critical Vulnerability: CVE-2026-23240 — linux — linux_kernel

In the Linux kernel, the following vulnerability has been resolved: tls: Fix race condition in tls_sw_cancel_work_tx() This issue was discovered during a code audit. After cancel_delayed_work_sync() is called from tls_sk_proto_close(), tx_work_handler() can still be scheduled from paths such as the Delayed ACK handler or ksoftirqd. As a result, the tx_work_handler() worker may dereference a freed TLS object. The following is a simple race scenario: cpu0 cpu

Wednesday, May 20, 2026linuxVulnios Threat Intelligence
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Vulnerability Snapshot

CVE-2026-23240 is rated CRITICAL — exploitation is trivial or already observed in the wild and impact is severe. Patch immediately, not on the next maintenance window.

Affected technology: linux_kernel.

Executive Summary

In the Linux kernel, the following vulnerability has been resolved:

tls: Fix race condition in tls_sw_cancel_work_tx()

This issue was discovered during a code audit.

After cancel_delayed_work_sync() is called from tls_sk_proto_close(),

tx_work_handler() can still be scheduled from paths such as the

Delayed ACK handler or ksoftirqd.

As a result, the tx_work_handler() worker may dereference a freed

TLS object.

The following is a simple race scenario:

cpu0 cpu1

tls_sk_proto_close()

tls_sw_cancel_work_tx()

tls_write_space()

tls_sw_write_space()

if (!test_and_set_bit(BIT_TX_SCHEDULED, &tx_ctx->tx_bitmask))

set_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask);

cancel_delayed_work_sync(&ctx->tx_work.work);

schedule_delayed_work(&tx_ctx->tx_work.work, 0);

To prevent this race condition, cancel_delayed_work_sync()

Why It Matters

CVE-2026-23240 is rated CRITICAL severity, requiring immediate attention from security teams.

CVSS Base Score: 9.8/10

EPSS (Exploit Prediction): 0.1% probability of exploitation in the next 30 days.

Affected Technologies

Vendors: linux

Products: linux_kernel

🛡️What Defenders Should Check

  • Check if you are affected — Review your asset inventory for products listed in CVE-2026-23240.
  • Apply available patches — Visit vendor advisories for the latest security updates.
  • Monitor for exploitation — Check your SIEM/IDS logs for related indicators.

    • Use Vulnios to continuously monitor your exposure to CVE-2026-23240 and similar vulnerabilities.

    References & Sources

  • https://git.kernel.org/stable/c/17153f154f80be2b47ebf52840f2d8f724eb2f3b
  • https://git.kernel.org/stable/c/7bb09315f93dce6acc54bf59e5a95ba7365c2be4
  • https://git.kernel.org/stable/c/854cd32bc74fe573353095e90958490e4e4d641b
  • https://git.kernel.org/stable/c/a5de36d6cee74a92c1a21b260bc507e64bc451de

    • How Vulnios Detects This

    Vulnios scans for this vulnerability using Trivy and Grype for CVE matching against your container images and OS package manifests. Run a scan against your environment to see whether you are exposed; findings are linked back to the original CVE record so triage starts with the patch path already known.

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    Affected Products

    linux_kernel

    Sources

    Related Threat Alerts

    Frequently Asked Questions

    What is CVE-2026-23240?

    CVE-2026-23240 is a critical-severity vulnerability tracked under the Common Vulnerabilities and Exposures program. In the Linux kernel, the following vulnerability has been resolved:

    tls: Fix race condition in tls_sw_cancel_work_tx()

    This issue was discovered during a code audit.

    After cancel_delayed_work_sync(

    Am I affected?

    Check whether your environment runs linux_kernel. If you operate any of those, treat yourself as in scope until you have evidence otherwise. A Vulnios scan will identify the exact assets carrying the affected version.

    How urgent is the response?

    Critical: do not wait for your normal patch cycle. Verify exposure today, apply the vendor patch immediately, and add detection rules for any post-exploit indicators.

    How do I remediate?

    Apply the vendor patch listed in the upstream advisory linked under Sources. If the patch is not yet available, follow the vendor-supplied workaround (often a config flag or feature disable) and add detections for the published exploit pattern in your SIEM. Re-scan after the patch lands to confirm the finding clears.

    Where can I track exploitation activity?

    Watch CISA's Known Exploited Vulnerabilities catalog for CVE-2026-23240. Cross-reference with public exploit databases and your own SIEM/IDS for indicator-of-compromise patterns. Vulnios tracks KEV status automatically and surfaces it on the asset findings view.

    How does Vulnios help with this?

    Vulnios continuously cross-references your asset inventory against the live CVE feed (NVD, vendor advisories, CISA KEV, and curated OSINT). When a new CVE matches your environment, you get a prioritized finding with the severity, KEV status, exploit-prediction (EPSS), and a direct path to the vendor patch. You can start a free scan from the homepage.

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