VulnerabilityPublished 9 Dec 2025Updated 30 Jul 2026

CVE-2025-40337: Linux kernel · net: stmmac: Correctly handle Rx checksum offload errors

Source GCVE Database

Not known to be exploited · CVSS 8.2 High.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score

8.2High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 41% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: High
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 9 Dec 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.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-4h2c-rg8h-8jqc

What to do

AI-suggested

A patch has been applied to the Linux kernel to correct the checksum offload error handling in the stmmac driver. Users should update to a kernel version that includes this fix. Since no explicit patch links or vendor advisories are provided, verify with the official Linux kernel release notes or vendor updates for the fixed version.

Description

A vulnerability in the Linux kernel's stmmac network driver caused it to incorrectly handle Rx checksum offload errors. The affected function, stmmac_rx, would mark packets as having valid checksums even when hardware reported checksum errors, potentially allowing corrupt packets to be processed by the network stack. This flaw has been corrected by ensuring the kernel checks the hardware status flag indicating checksum errors and forces software validation of such packets.

Impact

This vulnerability could allow corrupt network packets to be accepted as valid by the Linux kernel network stack, potentially leading to data integrity issues or denial of service conditions. The CVSS vector indicates no confidentiality impact, high integrity impact, and low availability impact. There are no known exploits in the wild at this time.

Summary

The Linux kernel's stmmac_rx function previously set skb->ip_summed to CHECKSUM_UNNECESSARY whenever hardware checksum offload was enabled and the packet was a known IP ethertype, without verifying if the hardware reported a checksum error. This omission meant that corrupt packets with checksum failures could be passed up the network stack as valid. The patch fixes this by checking the csum_none status flag, which the hardware sets when a checksum error occurs, and setting skb->ip_summed to CHECKSUM_NONE to trigger software checksum validation, preventing corrupt packets from being accepted as valid.

References

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