CVE-2021-47215

What it actually does

Race condition allows unprotected concurrent modifications to a list of TLS RX resync contexts, leading to list corruption during resync_handle_seq_match and napi handling.

Why it matters to the business

Systems may experience kernel crashes or instability during TLS receive operations, disrupting encrypted network traffic and requiring restarts.

How an attack unfolds

An attacker triggers specific TLS RX resync conditions that cause concurrent list access, corrupting the list structure and resulting in a crash when the NAPI handler processes entries.

How to fix it

Update to a kernel version containing commit that protects TLS context list entries until resync handling completes; apply the fix referenced in c1ad7111a090adfcd5898af40724907adc987acf for affected mlx5e kTLS code paths.

How to confirm the fix worked

Confirm kernel source includes protection around resync context list operations; test TLS RX resync flows under concurrent load to verify absence of list corruption or crashes.

Typical attack path

1. Establish TLS connection to target system using mlx5e driver
2. Force RX resync sequence number matches
3. Induce timing where resync_handle_seq_match runs concurrently with list processing
4. Trigger kernel panic from corrupted list

How to detect it

Inspect kernel logs for crashes or warnings during TLS RX processing; look for evidence of list corruption in network stack traces after publication date.

What your security team should do

• Prioritize kernel updates on systems using mlx5e with kTLS RX
• Monitor for related stability issues in TLS traffic
• Review EPSS trend for any increase in exploit likelihood