CVE-2025-38488

What it actually does

Use-after-free in smb:client crypt_message() when hardware crypto accelerators return -EINPROGRESS from crypto_aead_encrypt/decrypt; the creq buffer is freed before the async operation completes, allowing later driver access to freed memory and resulting in NULL pointer dereferences or kernel crashes.

Why it matters to the business

Kernel instability and crashes on systems using SMB with hardware crypto acceleration can cause denial of service, unplanned reboots, and loss of availability for file services; low EPSS and no KEV status reduce immediate urgency but long publication window and listed threat actors increase monitoring priority.

How an attack unfolds

An attacker with network access to an SMB client initiates encrypted sessions that invoke async AEAD operations via hardware accelerators; the missing crypto_wait_req allows the request buffer to be freed while the operation is pending, leading to use-after-free when the driver later accesses it. Threat actors such as Advanced Spyware Campaign and VMSCAPE have been associated with similar Linux kernel issues, though exploit maturity remains none.

How to fix it

Update to fixed kernel versions that restore DECLARE_CRYPTO_WAIT, aead_request_set_callback, and crypto_wait_req handling in crypt_message; for listed Debian packages apply the exact fixed versions: thunderbird 1:128.13.0esr-1~deb11u1 (Debian 11), 1:128.13.0esr-1~deb12u1 (Debian 12), 1:128.13.0esr-1 (Debian 13) and equivalent firefox-esr 128.13.0esr packages.

How to confirm the fix worked

Confirm kernel version contains the async crypto restoration; test SMB sessions with hardware crypto modules enabled and verify no crashes occur on -EINPROGRESS returns; review crypto_alloc_aead calls to ensure proper wait handling.

Typical attack path

1. Establish SMB connection requiring crypto operations
2. Trigger hardware-accelerated AEAD encrypt/decrypt returning -EINPROGRESS
3. Force immediate kvfree_sensitive on creq while async work is queued
4. Wait for hardware driver callback to dereference freed memory
5. Induce kernel crash or attempt further memory corruption

How to detect it

Search kernel logs for oops, NULL pointer dereference, or use-after-free messages during SMB client crypto operations; correlate with hardware crypto driver activity and review threat actor patterns from Advanced Spyware Campaign or VMSCAPE for similar kernel exploitation attempts.

What your security team should do

• Prioritize kernel and affected package updates within standard change windows given low EPSS and no KEV status
• Monitor for kernel oops or NULL dereference logs during SMB activity
• Disable hardware crypto accelerators temporarily if crashes are observed
• Track EPSS trend and threat actor mentions for any increase in activity