Linux Kernel up to 6.16.9 sun4i_can ndo_change_mtu buffer overflow

CVSS Meta Temp Score
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CTI Interest Score
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7.6$0-$5k0.00

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.16.9. It has been declared as critical. This vulnerability affects the function ndo_change_mtu of the component sun4i_can. Such manipulation leads to buffer overflow. This vulnerability is listed as CVE-2025-39986. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 6.16.9. Affected by this issue is the function ndo_change_mtu of the component sun4i_can. The manipulation with an unknown input leads to a buffer overflow vulnerability. Using CWE to declare the problem leads to CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: can: sun4i_can: populate ndo_change_mtu() to prevent buffer overflow Sending an PF_PACKET allows to bypass the CAN framework logic and to directly reach the xmit() function of a CAN driver. The only check which is performed by the PF_PACKET framework is to make sure that skb->len fits the interface's MTU. Unfortunately, because the sun4i_can driver does not populate its net_device_ops->ndo_change_mtu(), it is possible for an attacker to configure an invalid MTU by doing, for example: $ ip link set can0 mtu 9999 After doing so, the attacker could open a PF_PACKET socket using the ETH_P_CANXL protocol: socket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL)) to inject a malicious CAN XL frames. For example: struct canxl_frame frame = { .flags = 0xff, .len = 2048, }; The CAN drivers' xmit() function are calling can_dev_dropped_skb() to check that the skb is valid, unfortunately under above conditions, the malicious packet is able to go through can_dev_dropped_skb() checks: 1. the skb->protocol is set to ETH_P_CANXL which is valid (the function does not check the actual device capabilities). 2. the length is a valid CAN XL length. And so, sun4ican_start_xmit() receives a CAN XL frame which it is not able to correctly handle and will thus misinterpret it as a CAN frame. This can result in a buffer overflow. The driver will consume cf->len as-is with no further checks on this line: dlc = cf->len; Here, cf->len corresponds to the flags field of the CAN XL frame. In our previous example, we set canxl_frame->flags to 0xff. Because the maximum expected length is 8, a buffer overflow of 247 bytes occurs a couple line below when doing: for (i = 0; i < dlc; i++) writel(cf->data[i], priv->base + (dreg + i * 4)); Populate net_device_ops->ndo_change_mtu() to ensure that the interface's MTU can not be set to anything bigger than CAN_MTU. By fixing the root cause, this prevents the buffer overflow.

The advisory is shared for download at git.kernel.org. This vulnerability is handled as CVE-2025-39986 since 04/16/2025. The exploitation is known to be easy. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 02/08/2026).

The vulnerability scanner Nessus provides a plugin with the ID 271541 (Linux Distros Unpatched Vulnerability : CVE-2025-39986), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.4.300, 5.10.245, 5.15.194, 6.1.155, 6.6.109, 6.12.50 or 6.16.10 eliminates this vulnerability. Applying the patch 063539db42203b29d5aa2adf0cae3d68c646a6b6/4f382cc887adca8478b9d3e6b81aa6698a95fff4/60463a1c138900494cb3adae41142a11cd8feb3c/a61ff7ac93270d20ca426c027d6d01c8ac8e904c/2e423e1990f3972cbea779883fef52c2f2acb858/de77841652e57afbc46e9e1dbf51ee364fc008e1/7f7b21026a6febdb749f6f6f950427245aa86cce/61da0bd4102c459823fbe6b8b43b01fb6ace4a22 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (271541) and CERT Bund (WID-SEC-2025-2298). Once again VulDB remains the best source for vulnerability data.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • RESF Rocky Linux
  • Open Source Linux Kernel
  • IBM QRadar SIEM
  • Dell NetWorker

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.0
VulDB Meta Temp Score: 7.6

VulDB Base Score: 8.0
VulDB Temp Score: 7.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Buffer overflow
CWE: CWE-120 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 271541
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2025-39986

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.4.300/5.10.245/5.15.194/6.1.155/6.6.109/6.12.50/6.16.10
Patch: 063539db42203b29d5aa2adf0cae3d68c646a6b6/4f382cc887adca8478b9d3e6b81aa6698a95fff4/60463a1c138900494cb3adae41142a11cd8feb3c/a61ff7ac93270d20ca426c027d6d01c8ac8e904c/2e423e1990f3972cbea779883fef52c2f2acb858/de77841652e57afbc46e9e1dbf51ee364fc008e1/7f7b21026a6febdb749f6f6f950427245aa86cce/61da0bd4102c459823fbe6b8b43b01fb6ace4a22

Timelineinfo

04/16/2025 CVE reserved
10/15/2025 +182 days Advisory disclosed
10/15/2025 +0 days VulDB entry created
02/08/2026 +116 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-39986 (🔒)
GCVE (CVE): GCVE-0-2025-39986
GCVE (VulDB): GCVE-100-328628
CERT Bund: WID-SEC-2025-2298 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 10/15/2025 12:05
Updated: 02/08/2026 20:15
Changes: 10/15/2025 12:05 (59), 10/27/2025 15:49 (2), 11/03/2025 18:47 (7), 11/22/2025 16:50 (1), 12/21/2025 07:39 (1), 02/08/2026 20:15 (1)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

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