CVE-2026-23240: tls: Fix race condition in tls_sw_cancel_work_tx()

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-10 · updated 2026-10-19
Weakness: CWE-362

Description

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() is replaced with disable_delayed_work_sync().

Affected products

Linux kernel: from 5.3.1 before 6.12.75; from 6.13 before 6.18.16; from 6.19 before 6.19.6; 5.3, 5.3-rc4, 5.3-rc5, 5.3-rc6, 5.3-rc7, 5.3-rc8 (+1) — fixed in 6.12.75, 6.18.16, 6.19.6

How to fix

Upgrade to a fixed version: Linux kernel 6.12.75, 6.18.16, 6.19.6. Check the vendor advisory for mitigations.

References

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