CVE-2025-21704: linux kernel Memory Corruption

Description

In the Linux kernel, the following vulnerability has been resolved: usb: cdc-acm: Check control transfer buffer size before access If the first fragment is shorter than struct usb_cdc_notification, we can't calculate an expected_size. Log an error and discard the notification instead of reading lengths from memory outside the received data, which can lead to memory corruption when the expected_size decreases between fragments, causing `expected_size - acm->nb_index` to wrap. This issue has been present since the beginning of git history; however, it only leads to memory corruption since commit ea2583529cd1 ("cdc-acm: reassemble fragmented notifications"). A mitigating factor is that acm_ctrl_irq() can only execute after userspace has opened /dev/ttyACM*; but if ModemManager is running, ModemManager will do that automatically depending on the USB device's vendor/product IDs and its other interfaces.

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CVSS v3.1 Score

7.8

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-787 Out-of-bounds Write

Affected Products

Vendor	Product	Versions
linux	linux_kernel	2.6.13 — 5.4.291
linux	linux_kernel	5.5 — 5.10.235
linux	linux_kernel	5.11 — 5.15.179
linux	linux_kernel	5.16 — 6.1.129
linux	linux_kernel	6.2 — 6.6.79
linux	linux_kernel	6.7 — 6.12.16
linux	linux_kernel	6.13 — 6.13.4
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/383d516a0ebc8641372b521c8cb717f0f1834831 https://git.kernel.org/stable/c/6abb510251e75f875797d8983a830e6731fa281c https://git.kernel.org/stable/c/7828e9363ac4d23b02419bf2a45b9f1d9fb35646 https://git.kernel.org/stable/c/871619c2b78fdfe05afb4e8ba548678687beb812 https://git.kernel.org/stable/c/90dd2f1b7342b9a671a5ea4160f408037b92b118 https://git.kernel.org/stable/c/a4e1ae5c0533964170197e4fb4f33bc8c1db5cd2 https://git.kernel.org/stable/c/e563b01208f4d1f609bcab13333b6c0e24ce6a01 https://git.kernel.org/stable/c/f64079bef6a8a7823358c3f352ea29a617844636

Exploits

https://project-zero.issues.chromium.org/issues/395107243

Other References

https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html https://cert-portal.siemens.com/productcert/html/ssa-265688.html

Frequently Asked Questions

What is CVE-2025-21704? +

In the Linux kernel, the following vulnerability has been resolved: usb: cdc-acm: Check control transfer buffer size before access If the first fragment is shorter than struct usb_cdc_notification, we can't calculate an expected_size. Log an error and discard the notification instead of reading lengths from memory outside the received data, which can lead to memory corruption when the expected_size decreases between fragments, causing `expected_size - acm->nb_index` to wrap. This issue has been present since the beginning of git history; however, it only leads to memory corruption since commit ea2583529cd1 ("cdc-acm: reassemble fragmented notifications"). A mitigating factor is that acm_ctrl_irq() can only execute after userspace has opened /dev/ttyACM*; but if ModemManager is running, ModemManager will do that automatically depending on the USB device's vendor/product IDs and its other interfaces. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2025-21704? +

CVE-2025-21704 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-21704? +

CVE-2025-21704 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-21704? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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