high CVSS 7.8

CVE-2024-26936·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate request buffer size in smb2_allocate_rsp_buf() The response buffer should be allocated in smb2_allocate_rsp_buf before validating request. But the fields in payload as well as smb2 header is used in smb2_allocate_rsp_buf(). This patch add simple buffer size validation to avoid potencial out-of-bounds in request buffer.

Severity
high
Software
Kernel
Fixed in
6.8.8
Published
2024-05-01

Affected versions

From: 6.7

Until: 6.8.8

Fixed in: 6.8.8

How to fix this CVE

Update your Linux kernel to version 6.8.8 or later to patch a buffer validation flaw in the SMB2 protocol handler (ksmbd). This vulnerability allows local attackers with standard user privileges to trigger out-of-bounds memory access by sending specially crafted SMB2 requests. Apply the kernel update immediately and reboot your system to ensure the fix is active.

sudo dnf update kernel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Check your kernel version: uname -r — if the output shows 6.7.x through 6.8.7, your system is vulnerable
  2. Verify ksmbd (SMB server) is loaded: lsmod | grep ksmbd — if present, the affected component is active
  3. Search kernel logs for SMB2 allocation errors: grep -i 'smb2_allocate_rsp_buf\|buffer.*overflow' /var/log/kern.log or journalctl -k | grep -i smb2
  4. Confirm the patch is installed after update: uname -r should show 6.8.8 or later; verify with: grep 'smb2_allocate_rsp_buf' /boot/System.map-$(uname -r) to ensure the patched symbol exists

FAQ

What is CVE-2024-26936?

A buffer validation vulnerability in the Linux kernel's SMB2 server implementation (ksmbd) that fails to properly validate request buffer sizes before dereferencing payload fields, potentially leading to out-of-bounds memory access and privilege escalation from unprivileged local users.

Is CVE-2024-26936 being actively exploited?

No, this vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) database and no public exploits are currently available, though the high CVSS score warrants prompt patching as a precaution.

What versions of Kernel are affected by CVE-2024-26936?

Linux kernel versions 6.7.x through 6.8.7 are vulnerable; kernel 6.8.8 and later versions contain the fix.

How do I check if my server is vulnerable to CVE-2024-26936?

Run uname -r and check if the output is between 6.7.0 and 6.8.7; if so, verify ksmbd is enabled with lsmod | grep ksmbd — if both conditions are true, your system is vulnerable.

Does Defensia detect CVE-2024-26936?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2024-26936 will appear in your dashboard with remediation steps.

Related Kernel CVEs

CVE-2026-64439CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: crypto: krb5 - filter out async aead implementations at alloc krb5_aead_encrypt(), krb5_aead_decrypt() in rfc3961_simplified.c and rfc8009_encrypt(), rfc8009_decrypt() in rfc8009_aes2.c set a NULL completion callback and treat any negative return from crypto_aead_{encrypt,decrypt}() as terminal, falling through to kfree_sensitive(buffer). When the encrypt_name resolves to an async AEAD instance the request returns -EINPROGRESS, the buffer is freed while the backend's worker still holds a pointer, and the worker dereferences the freed slab on completion. KASAN report under UML+SLUB with a synthetic async aead backend bound to krb5->encrypt_name: BUG: KASAN: slab-use-after-free in t5_stub_complete+0x7d/0xc7 The helpers were written synchronously, so filter the async instances out at allocation time instead of plumbing crypto_wait_req() through every call site. Reachable via net/rxrpc/rxgk.c, fs/afs/cm_security.c and net/ceph/crypto.c on systems with an async AEAD provider bound to the krb5 enctype name.
CVE-2026-100075CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: RDMA/srpt: Fix srpt_alloc_rw_ctxs() unwind counters When srpt_alloc_rw_ctxs() fails partway through a multi-buffer indirect descriptor, the unwind path destroys RDMA contexts but leaves stale n_rw_ctx and n_rdma values (and a dangling rw_ctxs pointer). Later sq_wr_avail accounting in srpt_queue_response() or srpt_write_pending() can then subtract the wrong number of send queue credits. Reset the counters and clear rw_ctxs after freeing the heap allocation before returning an error.
CVE-2026-64383CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: smb: client: fix double-free in SMB2_flush() replay SMB2_flush() keeps its response buffer bookkeeping across replay attempts. If a replayable flush response is received and the retry then fails before cifs_send_recv() stores a replacement response, flush_exit will free the stale response pointer a second time. Reinitialize resp_buftype and rsp_iov at the top of the replay loop so cleanup only acts on response state produced by the current attempt. This fixes a double-free without changing replay handling for successful requests.
CVE-2026-64385CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: smb: client: fix double-free in SMB2_ioctl() replay A response-bearing attempt can return a replayable error and free its response buffer. If SMB2_ioctl_init() fails before the next send, cleanup retains the previous buffer type and frees that response again. Reset response bookkeeping before each attempt to prevent the stale free.
CVE-2026-64384CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: smb: client: fix change notify replay double-free A response-bearing attempt can return a replayable error and free its response buffer. If SMB2_notify_init() fails before the next send, cleanup retains the previous buffer type and frees that response again. Reset response bookkeeping before each attempt to prevent the stale free.

References

Track CVEs across your fleet automatically

Defensia scans your Linux servers and tells you exactly which ones are running vulnerable versions — including CVE-2024-26936. Free for 1 server.

Get started free