CVE-2026-80637

A flaw was found in the Linux kernel's netfilter synproxy component. This vulnerability is due to unaligned memory access when adjusting timestamp fields. An attacker could potentially trigger this flaw by sending specially crafted network traffic, leading to performance degradation or a system crash, resulting in a Denial of Service (DoS).

Red Hat Enterprise Linux is affected by a moderate-severity denial of service flaw in the Linux kernel's netfilter SYNPROXY implementation, where TCP timestamp option fields are read and written through direct 32-bit dereferences that may be unaligned. A remote attacker who can reach a system with a SYNPROXY rule configured can send specially crafted TCP packets containing timestamp options through the SYNPROXY path, triggering an unaligned memory access that can crash the kernel on architectures that enforce strict alignment, or degrade performance elsewhere; there is no impact on confidentiality or integrity. The kernel and kernel-rt packages in Red Hat Enterprise Linux 7, 8, 9, and 10 are affected, with fixes currently deferred to a future update; the residual risk is a remote denial of service limited to systems where a SYNPROXY rule is actively configured. Red Hat Enterprise Linux 6 Extended Lifecycle Support and Red Hat In-Vehicle OS offerings are not affected because the vulnerable code is not present in those products. Red Hat rates this flaw Moderate severity (CVSS 5.5), lower than the Important rating (CVSS 7.5) in the upstream CVE record, because triggering the flaw requires a SYNPROXY rule to be configured on the affected system.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.