CVE-2026-80793
Description
A flaw was found in the Linux kernel's IPv4 fragmentation handling. When processing IPv4 packets, if the Maximum Transmission Unit (MTU) is set to an unusually small value, the kernel's fragmentation logic can enter an infinite loop. This loop causes the system to continuously allocate and transmit empty packet headers, leading to a system freeze or crash, effectively a Denial of Service (DoS). A remote attacker could exploit this by sending specially crafted network packets with a small MTU.
Statement
IPv4 fragmentation can enter a non progressing loop when ip_do_fragment() receives an effective MTU smaller than the IPv4 header length plus 8 bytes. In that case ip_frag_next() can compute a zero length fragment payload, while the fragmentation state does not advance and the kernel keeps allocating and transmitting header only fragments until a CPU soft lockup occurs. For the CVSS the PR:N is used in the paranoid network scenario because a remote sender does not need authenticated privileges if the vulnerable forwarding route or undersized device MTU already exists. The issue is network reachable only under specific routing or device MTU conditions, such as an MTU around 20, so AC:H is appropriate. Impact is denial of service via CPU soft lockup and possible kernel panic depending on watchdog policy. No confidentiality or integrity impact is indicated because the primitive is a non progressing loop rather than memory corruption.
Mitigation
Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.1 | N/A | N/A |
| Attack Vector | Local | N/A | N/A |
| Attack Complexity | High | N/A | N/A |
| Privileges Required | None | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | None | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
If an attacker can trigger the allocation of the limited resources, but the number or size of the resources is not controlled, then the most common result is denial of service. This would prevent valid users from accessing the product, and it could potentially have an impact on the surrounding environment, i.e., the product may slow down, crash due to unhandled errors, or lock out legitimate users. For example, a memory exhaustion attack against an application could slow down the application as well as its host operating system.
Access Control,Other
Technical Impact: Bypass Protection Mechanism; Other
In some cases it may be possible to force the product to "fail open" in the event of resource exhaustion. The state of the product -- and possibly the security functionality - may then be compromised.
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