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CVE-2026-31617— usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()

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ncm_unwrap_ntb中未验证最小block_len，可能导致整数下溢和内存泄漏。

AI Predicted 8.6 Difficulty: Moderate EPSS 0.18% · P7

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 30

VendorProduct Version RangeStatus
Linux Linux 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52< 068a7f2749fff6462a0a908ec415b885fe430f50 affected
2b74b0a04d3e9f9f08ff026e5663dce88ff94e52< 1425655c2870054c3ab4712e2b6dbdd331597ada affected
2b74b0a04d3e9f9f08ff026e5663dce88ff94e52< 8b3b7bd3c02f98634baaf36c7fc7ac915f6517ca affected
2b74b0a04d3e9f9f08ff026e5663dce88ff94e52< 0f156bb5334e588034ca68ac2ee92b23f66e56e7 affected
2b74b0a04d3e9f9f08ff026e5663dce88ff94e52< 8757a2593631443648218244b9788e193ae0fdc1 affected
2b74b0a04d3e9f9f08ff026e5663dce88ff94e52< 6762f8a95772265dd0c2ffe7f400493f3115b135 affected
2b74b0a04d3e9f9f08ff026e5663dce88ff94e52< d58ba8f6546232f8414f396c189297dbee03f1a7 affected
2b74b0a04d3e9f9f08ff026e5663dce88ff94e52< 74908b0318d1df1188457040b8714ff4d4b68126 affected
… +22 more rows
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I. Basic Information for CVE-2026-31617

Vulnerability Information
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Vulnerability Title
usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb() The block_len read from the host-supplied NTB header is checked against ntb_max but has no lower bound. When block_len is smaller than opts->ndp_size, the bounds check of: ndp_index > (block_len - opts->ndp_size) will underflow producing a huge unsigned value that ndp_index can never exceed, defeating the check entirely. The same underflow occurs in the datagram index checks against block_len - opts->dpe_size. With those checks neutered, a malicious USB host can choose ndp_index and datagram offsets that point past the actual transfer, and the skb_put_data() copies adjacent kernel memory into the network skb. Fix this by rejecting block lengths that cannot hold at least the NTB header plus one NDP. This will make block_len - opts->ndp_size and block_len - opts->dpe_size both well-defined. Commit 8d2b1a1ec9f5 ("CDC-NCM: avoid overflow in sanity checking") fixed a related class of issues on the host side of NCM.
Source: CVE Program / CVE List V5
CVSS Information
N/A
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ncm_unwrap_ntb中未验证最小block_len，可能导致整数下溢和内存泄漏。
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 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 ~ 068a7f2749fff6462a0a908ec415b885fe430f50 -
Linux Linux 5.9 -

II. Public POCs for CVE-2026-31617

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III. Intelligence Information for CVE-2026-31617

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Patches & Fixes for CVE-2026-31617 (5)

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-2026-31608 9.8 CRITICAL smb: server: avoid double-free in smb_direct_free_sendmsg after smb_direct_flush_send_list
CVE-2026-31633 9.8 CRITICAL rxrpc: Fix integer overflow in rxgk_verify_response()
CVE-2026-31536 9.8 CRITICAL smb: server: let send_done handle a completion without IB_SEND_SIGNALED
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-2026-31589 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-2026-31629 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-2026-31588 8.8 HIGH KVM: x86: Use scratch field in MMIO fragment to hold small write values
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-2026-31617

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