CVE-2026-98643

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix out-of-bounds read of rtt_min in sock_ops A sockops prog reading skops->rtt_min never checks the sk type: on the tcp_conn_request() path sock_ops->sk is a request_sock (non-full), and the ctx rewrite casts it to a tcp_sock (full) and reads rtt_min past the end of the request_sock, returning dirty adjacent memory. SEC("sockops") int prog(struct bpf_sock_ops *skops) { switch (skops->op) { case BPF_SOCK_OPS_RWND_INIT: leak = skops->rtt_min; /* reads the request_sock OOB */ ... } } For instance one such read returned rtt_min=0xffff8881, the high half of a leaked kernel pointer. Guarding that cast is exactly what SOCK_OPS_GET_FIELD() does -- it checks is_locked_tcp_sock and returns 0 when sock_ops->sk is not a locked full socket. Every other tcp_sock field in sock_ops goes through it; rtt_min is the only one open-coded, so it skips the check. Read rtt_min through SOCK_OPS_GET_FIELD() too. rtt_min is a bit special: it is a struct minmax and we only want the current min, so pass rtt_min.s[0].v. That is equivalent to the old hand-computed offset offsetof(struct tcp_sock, rtt_min) + sizeof_field(struct minmax_sample, t) (s[0] sits at rtt_min + 0 and .v at + sizeof(.t), i.e. what minmax_get() returns), so the loaded field is unchanged and only the full-sock guard is added. The two BUILD_BUG_ON()s that protected the hand-computed offset are no longer needed. Before patch: 0: r1 = *(u64 *)(r1 +0) ; r1 = skops->sk 1: r1 = *(u32 *)(r1 +2324) ; ((tcp_sock *)sk)->rtt_min.s[0].v After patch: 0: *(u64 *)(r1 +56) = r9 1: r9 = *(u8 *)(r1 +50) ; is_locked_tcp_sock 2: if r9 == 0 goto pc+4 ; not a locked full sock -> 0 3: r9 = *(u64 *)(r1 +56) 4: r1 = *(u64 *)(r1 +0) ; r1 = skops->sk 5: r1 = *(u32 *)(r1 +2324) ; rtt_min.s[0].v 6: goto pc+2 7: r9 = *(u64 *)(r1 +56) 8: r1 = 0

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CVSS version: CVSS v4.0

References

• MITRE
• NVD
• Launchpad
• Debian

Related Ubuntu Security Notices (USN)

• USN-8961-1
• Linux kernel vulnerabilities
• 3 November 2026
• USN-8959-1
• Linux kernel vulnerabilities
• 3 November 2026
• USN-8963-1
• Linux kernel (NVIDIA Tegra) vulnerabilities
• 3 November 2026
• USN-8960-1
• Linux kernel (OEM) vulnerabilities
• 3 November 2026

Other references

• https://www.cve.org/CVERecord?id=CVE-2026-98643
• https://git.kernel.org/stable/c/fc9d0e6e9d86fbefe7b8fe6ee49f4cf102add79d
• https://git.kernel.org/stable/c/fd6bf2721933d8c90bc4ce57f3e204c9295e7e3f
• https://git.kernel.org/stable/c/cba54d142c43ec96d8c4d566f66439e8c0afded7
• https://git.kernel.org/stable/c/75f8cf22463d82bb1fb0239a3d485fc8f4c8ef03
• https://git.kernel.org/stable/c/a8a9becbac93a9f54f4d565f1f3005eb08a7912f
• https://git.kernel.org/stable/c/3a46f14e6cf375f3ca38f8f6e6524749e24ea0a8
• https://git.kernel.org/stable/c/6785313d4fac96afb21ef193610c1fa88b1a9e64
• https://git.kernel.org/stable/c/0c796efa919f52f788c22c79d1f1b70321696b3d