CVE-2026-53249
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk8th percentile — higher than 8% of all known CVEs
Summary
In the Linux kernel, the ability to set IP LSRR and SSRR options has been restricted to users with CAP_NET_RAW capability. This prevents unprivileged applications from forcing packet routing through attacker-controlled nodes to leak TCP ISN and other protocol information.
Risk Assessment
The organization is at risk of leaking sensitive protocol data (e.g., TCP ISN) by unprivileged processes that can manipulate packet routing, facilitating man-in-the-middle attacks or session hijacking.
Recommendation
Update the Linux kernel to the patched version as soon as possible. Additionally, consider filtering LSRR/SSRR options on edge routers as recommended by RFC 7126.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: ipv4: restrict IPOPT_SSRR and IPOPT_LSRR options This patch restricts setting Loose Source and Record Route (LSRR) and Strict Source and Record Route (SSRR) IP options to users with CAP_NET_RAW capability. This prevents unprivileged applications from forcing packets to route through attacker-controlled nodes to leak TCP ISN and possibly other protocol information. While LSRR and SSRR are commonly filtered in many network environments, they may still be supported and forwarded along some network paths. RFC 7126 (Recommendations on Filtering of IPv4 Packets Containing IPv4 Options) recommend to drop these options in 4.3 and 4.4.