Security readout for executives and security teams
Plain-English summary
CVE-2025-21776 is a Linux kernel USB hub handling flaw. A malformed, non-compliant USB hub device can trigger a kernel fault when processed. The documented impact is system instability or crash risk, not confirmed remote compromise. Exposure is most relevant where untrusted USB devices can be connected or passed into Linux systems.
Executive priority
Treat this as a targeted stability risk rather than an internet-scale emergency. Prioritize patched kernels on systems with exposed USB ports, labs, kiosks, industrial devices, or virtualized environments that allow USB device passthrough.
Technical view
The Linux USB hub driver can bind to interface 1 on a non-compliant hub with multiple interfaces, while usb_hub_to_struct_hub() expects interface 0. This can cause NULL or inappropriate pointer dereference during hub probing. The upstream resolution rejects hub devices with more than one configuration or interface.
Likely exposure
Linux systems, appliances, and embedded products using affected kernel branches are potentially exposed if they process untrusted malformed USB hub devices. Systems with controlled physical access and no USB passthrough have lower practical exposure.
Exploitation context
The source describes a test program causing a kernel oops. KEV is false, and the provided sources do not report active exploitation. Evidence supports malformed-device-triggered kernel fault risk, but not proven widespread exploitation or remote attackability.
Researcher notes
The evidence points to a USB core hub parsing and binding issue fixed by rejecting non-compliant hub descriptors. No CVSS, CWE, or exploit-in-the-wild evidence is provided. Validate branch-specific status through upstream stable commits and downstream vendor backports.
Mitigation direction
- Update Linux kernels using vendor or distribution guidance that includes the referenced stable fixes.
- Apply Debian LTS kernel updates where Debian advisories apply.
- Restrict untrusted USB device access on sensitive Linux systems.
- Review Siemens advisories if using affected Siemens products.
- Check vendor guidance for embedded or appliance kernels before deploying fixes.
Validation and detection
- Inventory Linux kernel versions across servers, workstations, appliances, and embedded systems.
- Confirm whether kernels include the referenced USB hub stable commits or vendor backports.
- Review physical and virtual USB exposure, including device passthrough policies.
- Check Debian and Siemens advisories for product-specific applicability.
- Monitor logs for kernel oops events involving USB hub probing.
Public sources used
- CVE Program
- CVE List V5
- Linux stable commit 49f077106fa0
- Linux stable commit d343fe0fad5c
- Linux stable commit d3a67adb365c
- Linux stable commit c3720b04df84
- Linux stable commit e905a0fca7bf
- Linux stable commit 62d8f4c5454d
- Linux stable commit 5b9778e1fe71
- Linux stable commit 2240fed37afb
- Debian LTS advisory May 2025
- Debian LTS advisory March 2025
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2025-21776 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/49f077106fa07919a6a6dda99bb490dd1d1a8218CVE reference, Linux
- https://git.kernel.org/stable/c/d343fe0fad5c1d689775f2dda24a85ce98e29566CVE reference, Linux
- https://git.kernel.org/stable/c/d3a67adb365cdfdac4620daf38a82e57ca45806cCVE reference, Linux
- https://git.kernel.org/stable/c/c3720b04df84b5459050ae4e03ec7d545652f897CVE reference, Linux
- https://git.kernel.org/stable/c/e905a0fca7bff0855d312c16f71e60e1773b393eCVE reference, Linux
- https://git.kernel.org/stable/c/62d8f4c5454dd39aded4f343720d1c5a1803cfefCVE reference, Linux
- https://git.kernel.org/stable/c/5b9778e1fe715700993ce436c152dc3b7df0b490CVE reference, Linux
- https://git.kernel.org/stable/c/2240fed37afbcdb5e8b627bc7ad986891100e05dCVE reference, Linux
- https://lists.debian.org/debian-lts-announce/2025/05/msg00030.htmlCVE reference, CVE
- https://lists.debian.org/debian-lts-announce/2025/03/msg00028.htmlCVE reference, CVE
- https://cert-portal.siemens.com/productcert/html/ssa-265688.htmlCVE reference, siemens-SADP
- https://cert-portal.siemens.com/productcert/html/ssa-503939.htmlCVE reference, siemens-SADP
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.