CVE-2025-39987: Linux kernel · can: hi311x: populate ndo_change_mtu() to prevent buffer overflow
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High · fixed in 5.15.0-1110.119~20.04.1 : patch Linux kernel soon.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.15.0-1110.119~20.04.1, 5.15.0-1100.109~20.04.1, 5.15.0-1100.107~20.04.2 +2
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 15 Oct 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| linux-azure | Affected
| Fixed in
|
AI-suggested
A fix is available that populates the net_device_ops->ndo_change_mtu() function in the hi311x CAN driver to prevent setting MTU values larger than CAN_MTU. Applying this fix prevents the buffer overflow by enforcing valid MTU limits. Users should update their Linux kernel to a version that includes this patch. No additional mitigations are indicated.
Description
In the Linux kernel, the following vulnerability has been resolved: can: hi311x: 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, hi3110_hard_start_xmit() receives a CAN XL frame which it is not able to correctly handle and will thus misinterpret it as a CAN frame. The driver will consume frame->len as-is with no further checks. This can result in a buffer overflow later on in hi3110_hw_tx() on this line: memcpy(buf + HI3110_FIFO_EXT_DATA_OFF, frame->data, frame->len); Here, frame->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! 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.
References
- nvd.nist.gov/vuln/detail/CVE-2025-39987 (opens in a new tab)
- git.kernel.org/stable/c/57d332ce8c921d0e340650470bb0c1d707f216ee (opens in a new tab)
- git.kernel.org/stable/c/7ab85762274c0fa997f0ef9a2307b2001aae43c4 (opens in a new tab)
- git.kernel.org/stable/c/8f351db6b2367991f0736b2cff082f5de4872113 (opens in a new tab)
- git.kernel.org/stable/c/ac1c7656fa717f29fac3ea073af63f0b9919ec9a (opens in a new tab)
- git.kernel.org/stable/c/be1b25005fd0f9d4e78bec6695711ef87ee33398 (opens in a new tab)
- git.kernel.org/stable/c/def814b4ba31b563584061d6895d5ff447d5bc14 (opens in a new tab)
- git.kernel.org/stable/c/e77fdf9e33a83a08f04ab0cb68c19ddb365a622f (opens in a new tab)
- git.kernel.org/stable/c/f2c247e9581024d8b3dd44cbe086bf2bebbef42c (opens in a new tab)
- ubuntu.com/security/CVE-2025-39987 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-39987 (opens in a new tab)
- git.kernel.org/linus/ac1c7656fa717f29fac3ea073af63f0b9919ec9a (opens in a new tab)
- ubuntu.com/security/notices/USN-8033-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8033-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8033-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8034-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8033-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8033-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-8034-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8033-6 (opens in a new tab)
- ubuntu.com/security/notices/USN-8033-7 (opens in a new tab)