high CVSS 7.1 EPSS <0.1%

CVE-2025-21742·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: usbnet: ipheth: use static NDP16 location in URB Original code allowed for the start of NDP16 to be anywhere within the URB based on the `wNdpIndex` value in NTH16. Only the start position of NDP16 was checked, so it was possible for even the fixed-length part of NDP16 to extend past the end of URB, leading to an out-of-bounds read. On iOS devices, the NDP16 header always directly follows NTH16. Rely on and check for this specific format. This, along with NCM-specific minimal URB length check that already exists, will ensure that the fixed-length part of NDP16 plus a set amount of DPEs fit within the URB. Note that this commit alone does not fully address the OoB read. The limit on the amount of DPEs needs to be enforced separately.

Severity
high
Software
Kernel
Fixed in
6.13.3
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at <0.1% — higher than 11% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2025-21742 scores 7.1 on CVSS, so a successful attack would be serious — but at <0.1%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

From: 6.13

Until: 6.13.3

Fixed in: 6.13.3

How to fix this CVE

Update the Linux kernel to version 6.13.3 or later to resolve an out-of-bounds read vulnerability in the ipheth USB driver. This vulnerability affects kernel versions 6.13 through 6.13.2 and allows potential memory disclosure through improper validation of USB Network Control Model (NCM) packet headers. Apply the update immediately to systems running affected kernel versions, especially those with iOS USB tethering support enabled.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check installed kernel version with `uname -r` and compare against 6.13.3 to determine if your system is vulnerable
  2. Step 2: Verify ipheth driver is loaded with `lsmod | grep ipheth` to confirm the vulnerable component is active
  3. Step 3: Check kernel logs for USB errors related to NCM packets with `dmesg | grep -i 'ipheth\|usb\|ncm'` to identify exploitation attempts
  4. Step 4: After patching, confirm the new kernel is running with `uname -r` and verify it shows version 6.13.3 or later

FAQ

What is CVE-2025-21742?

CVE-2025-21742 is an out-of-bounds read vulnerability in the Linux kernel's ipheth USB driver that fails to properly validate the position of Network Data Pointer (NDP16) headers, potentially allowing memory disclosure when processing specially crafted USB packets from tethered iOS devices.

Is CVE-2025-21742 being actively exploited?

No, CVE-2025-21742 is not currently listed as actively exploited by CISA, and no public exploits are available. However, the vulnerability should still be patched promptly due to its high severity rating.

What versions of Kernel are affected by CVE-2025-21742?

Linux kernel versions 6.13 through 6.13.2 are affected. The vulnerability is fixed in kernel version 6.13.3 and later.

How do I check if my server is vulnerable to CVE-2025-21742?

Run `uname -r` to display your kernel version. If it shows 6.13.0, 6.13.1, or 6.13.2, your system is vulnerable. Additionally, check if iOS tethering is in use with `lsmod | grep ipheth`.

Does Defensia detect CVE-2025-21742?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2025-21742 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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References

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