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CVE-2026-31538— smb: server: make use of smbdirect_socket.recv_io.credits.available

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于管理接收信用的逻辑存在竞争条件，可能导致授予不存在的信用。

CVSS 7.5 · High EPSS 0.61% · P48

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 8

VendorProduct Version RangeStatus
Linux Linux 89b021a72663c4d96d8a8b85272bb42d991a1c6f< 66c082e3d4651e8629a393a9e182b01eb50fb0a3 affected
89b021a72663c4d96d8a8b85272bb42d991a1c6f< 809cbd31aa4f87a1b889532244c9cf30eb022385 affected
89b021a72663c4d96d8a8b85272bb42d991a1c6f< 26ad87a2cfb8c1384620d1693a166ed87303046e affected
6.18 affected
< 6.18 unaffected
6.18.11≤ 6.18.* unaffected
6.19.1≤ 6.19.* unaffected
7.0≤ * unaffected
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I. Basic Information for CVE-2026-31538

Vulnerability Information
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Vulnerability Title
smb: server: make use of smbdirect_socket.recv_io.credits.available
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: smb: server: make use of smbdirect_socket.recv_io.credits.available The logic off managing recv credits by counting posted recv_io and granted credits is racy. That's because the peer might already consumed a credit, but between receiving the incoming recv at the hardware and processing the completion in the 'recv_done' functions we likely have a window where we grant credits, which don't really exist. So we better have a decicated counter for the available credits, which will be incremented when we posted new recv buffers and drained when we grant the credits to the peer. This fixes regression Namjae reported with the 6.18 release.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于管理接收信用的逻辑存在竞争条件，可能导致授予不存在的信用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 89b021a72663c4d96d8a8b85272bb42d991a1c6f ~ 66c082e3d4651e8629a393a9e182b01eb50fb0a3 -
Linux Linux 6.18 -

II. Public POCs for CVE-2026-31538

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III. Intelligence Information for CVE-2026-31538

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Same Patch Batch · Linux · 2026-04-24 · 138 CVEs total

CVE-2026-31649 9.8 CRITICAL net: stmmac: fix integer underflow in chain mode
CVE-2026-31607 9.8 CRITICAL usbip: validate number_of_packets in usbip_pack_ret_submit()
CVE-2026-31536 9.8 CRITICAL smb: server: let send_done handle a completion without IB_SEND_SIGNALED
CVE-2026-31633 9.8 CRITICAL rxrpc: Fix integer overflow in rxgk_verify_response()
CVE-2026-31669 9.8 CRITICAL mptcp: fix slab-use-after-free in __inet_lookup_established
CVE-2026-31668 9.8 CRITICAL seg6: separate dst_cache for input and output paths in seg6 lwtunnel
CVE-2026-31608 9.8 CRITICAL smb: server: avoid double-free in smb_direct_free_sendmsg after smb_direct_flush_send_list
CVE-2026-31589 9.8 CRITICAL mm: call ->free_folio() directly in folio_unmap_invalidate()
CVE-2026-31609 9.8 CRITICAL smb: client: avoid double-free in smbd_free_send_io() after smbd_send_batch_flush()
CVE-2026-31657 9.8 CRITICAL batman-adv: hold claim backbone gateways by reference
CVE-2026-31659 9.8 CRITICAL batman-adv: reject oversized global TT response buffers
CVE-2026-31637 9.8 CRITICAL rxrpc: reject undecryptable rxkad response tickets
CVE-2026-31636 9.1 CRITICAL rxrpc: fix RESPONSE authenticator parser OOB read
CVE-2026-31570 8.8 HIGH can: gw: fix OOB heap access in cgw_csum_crc8_rel()
CVE-2026-31558 8.8 HIGH LoongArch: KVM: Make kvm_get_vcpu_by_cpuid() more robust
CVE-2026-31553 8.8 HIGH KVM: arm64: Fix the descriptor address in __kvm_at_swap_desc()
CVE-2026-31588 8.8 HIGH KVM: x86: Use scratch field in MMIO fragment to hold small write values
CVE-2026-31629 8.8 HIGH nfc: llcp: add missing return after LLCP_CLOSED checks
CVE-2026-31622 8.8 HIGH NFC: digital: Bounds check NFC-A cascade depth in SDD response handler
CVE-2026-31611 8.6 HIGH ksmbd: require 3 sub-authorities before reading sub_auth[2]

Showing top 20 of 138 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-31538

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