high CVSS 7.8

CVE-2023-52757·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix potential deadlock when releasing mids All release_mid() callers seem to hold a reference of @mid so there is no need to call kref_put(&mid->refcount, __release_mid) under @server->mid_lock spinlock. If they don't, then an use-after-free bug would have occurred anyways. By getting rid of such spinlock also fixes a potential deadlock as shown below CPU 0 CPU 1 ------------------------------------------------------------------ cifs_demultiplex_thread() cifs_debug_data_proc_show() release_mid() spin_lock(&server->mid_lock); spin_lock(&cifs_tcp_ses_lock) spin_lock(&server->mid_lock) __release_mid() smb2_find_smb_tcon() spin_lock(&cifs_tcp_ses_lock) *deadlock*

Severity: high
Software: Kernel
Fixed in: 6.6.3
Published: 2024-05-21

Affected versions

From: 6.6

Until: 6.6.3

Fixed in: 6.6.3

How to fix this CVE

Update your Linux kernel to version 6.6.3 or later to resolve a critical deadlock vulnerability in the SMB client mid-release mechanism. This vulnerability can cause kernel hangs when concurrent operations access shared locking structures. Ensure systems running kernel versions 6.6 through 6.6.2 are patched immediately, particularly those relying on SMB/CIFS network file sharing.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

Step 1: Check current kernel version with 'uname -r' and compare against vulnerable range 6.6.0-6.6.2
Step 2: Verify SMB/CIFS kernel modules are loaded with 'lsmod | grep cifs'
Step 3: Search kernel logs for deadlock indicators: 'journalctl -xe | grep -i deadlock' or 'dmesg | grep -i "spinlock\|mid_lock"'
Step 4: After patching, confirm fixed version with 'uname -r' and verify it shows 6.6.3 or higher

FAQ

What is CVE-2023-52757?

CVE-2023-52757 is a kernel deadlock vulnerability in the Linux SMB client code where improper spinlock management during mid (message ID) release can cause circular lock dependencies between mid_lock and tcp_ses_lock, freezing affected systems.

Is CVE-2023-52757 being actively exploited?

No, this vulnerability is not listed in CISA's Known Exploited Vulnerabilities (KEV) catalog and no public exploits are available. However, it can be triggered by local attackers with low privileges.

What versions of Kernel are affected by CVE-2023-52757?

Linux kernel versions 6.6.0, 6.6.1, and 6.6.2 are vulnerable. Version 6.6.3 and all subsequent releases contain the fix.

How do I check if my server is vulnerable to CVE-2023-52757?

Run 'uname -r' to display your kernel version. If it returns a version between 6.6.0 and 6.6.2 inclusive, your system is vulnerable. Also confirm CIFS is in use with 'lsmod | grep cifs'.

Does Defensia detect CVE-2023-52757?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2023-52757 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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-2026-64439CVSS 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-2026-64055CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: net: ethernet: cortina: Carry over frag counter The gmac_rx() NAPI poll function assembles packets in an SKB from a ring buffer. If the ring buffer gets completely emptied during a poll cycle, we exit gmac_rx(), but the packet is not yet completely assembled in the SKB, yet the fragment counter frag_nr is reset to zero on the next invocation. Solve this by making the RX fragment counter a part of the port struct, and carry it over between invocations. Reset the fragment counter only right after calling napi_gro_frags(), on error (after calling napi_free_frags()) or if stopping the port. Reset it in some place where not strictly necessary just to emphasize what is going on. This was found by Sashiko during normal patch review.

CVE-2026-64397CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ksmbd: serialize QUERY_DIRECTORY requests per file smb2_query_dir() stores a pointer to its stack-allocated private data in the ksmbd_file readdir_data. Concurrent QUERY_DIRECTORY requests using the same file handle can overwrite this pointer while an iterate_dir() callback is still using it, resulting in a stack use-after-free. Add a per-file mutex and hold it while accessing the shared directory enumeration state. The lock covers scan restart, dot entry state, readdir_data setup and iteration, and response construction. This prevents another request from replacing readdir_data.private before the current request has finished using it and also serializes the shared file position.

CVE-2026-64056CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: net: ethernet: cortina: Make RX SKB per-port The SKB used to assemble packets from fragments in gmac_rx() is static local, but the Gemini has two ethernet ports, meaning there can be races between the ports on a bad day if a device is using both. Make the RX SKB a per-port variable and carry it over between invocations in the port struct instead. Zero the pointer once we call napi_gro_frags(), on error (after calling napi_free_frags()) or if the port is stopped. Zero it in some place where not strictly necessary just to emphasize what is going on. This was found by Sashiko during normal patch review.

References

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