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Vulnerability details: VCID-g9zj-fsa9-vkca
Vulnerability ID VCID-g9zj-fsa9-vkca
Aliases CVE-2026-31617
Summary 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.
Status Published
Exploitability 0.5
Weighted Severity 6.3
Risk 3.1
Affected and Fixed Packages Package Details
Weaknesses (1)
CWE-191 Integer Underflow (Wrap or Wraparound)
System Score Found at
cvssv3 7.0 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2026-31617.json
epss 0.00012 https://api.first.org/data/v1/epss?cve=CVE-2026-31617
epss 0.00018 https://api.first.org/data/v1/epss?cve=CVE-2026-31617
cvssv3.1 7.1 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2026-31617.json
https://api.first.org/data/v1/epss?cve=CVE-2026-31617
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-31617
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
2461448 https://bugzilla.redhat.com/show_bug.cgi?id=2461448
No exploits are available.
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2026-31617.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H Found at https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.01728
EPSS Score 0.00012
Published At April 29, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-04-25T23:21:34.811934+00:00 Debian Importer Import https://security-tracker.debian.org/tracker/data/json 38.4.0