high CVSS 7.1

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
2025-02-27

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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CVE-2026-64033CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: RDMA/rtrs: Fix use-after-free in path file creation cleanup In the error path of rtrs_srv_create_path_files(), the sysfs root folders may already have been created and srv_path->kobj may already have been initialized. If a later step fails, the cleanup currently calls kobject_put(&srv_path->kobj) before rtrs_srv_destroy_once_sysfs_root_folders(srv_path). kobject_put() may drop the last reference to srv_path->kobj and invoke the release callback, rtrs_srv_release(), which frees srv_path. The following call to rtrs_srv_destroy_once_sysfs_root_folders(srv_path) then dereferences srv_path internally to access srv_path->srv, resulting in a use-after-free. This failure path is reached before rtrs_srv_create_path_files() returns success, so the successful-path lifetime handling is not involved. Fix this by destroying the sysfs root folders before calling kobject_put(&srv_path->kobj), so srv_path is still valid while the helper accesses it. This issue was found by a static analysis tool I am developing.
CVE-2026-64007CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfilter: synproxy: refresh tcphdr after skb_ensure_writable synproxy_tstamp_adjust() rewrites the TCP timestamp option in place and then patches the TCP checksum via inet_proto_csum_replace4() on the caller-supplied tcphdr pointer. Both ipv4_synproxy_hook() and ipv6_synproxy_hook() obtain that pointer with skb_header_pointer() before calling in, so it may either alias skb->head directly or point at the caller's on-stack _tcph buffer. Between obtaining the pointer and using it, the function calls skb_ensure_writable(skb, optend), which on a cloned or non-linear skb invokes pskb_expand_head() and frees the old skb->head. After that point the cached th is stale: caller (ipv[46]_synproxy_hook) th = skb_header_pointer(skb, ..., &_tcph) synproxy_tstamp_adjust(skb, protoff, th, ...) skb_ensure_writable(skb, optend) pskb_expand_head() /* kfree(old skb->head) */ ... inet_proto_csum_replace4(&th->check, ...) /* writes into freed head, or into the caller's stack copy leaving the on-wire checksum stale */ The option bytes are written through skb->data and are fine; only the checksum update goes through th and so lands in the wrong place. The result is either a write into freed slab memory or a packet leaving with a checksum that does not match its payload. Fix by re-deriving th from skb->data + protoff immediately after skb_ensure_writable() succeeds, so the subsequent checksum update targets the linear, writable header.
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References

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