Linux kernel TCP UAF CVE-2026-98432 rated Critical
Original title: TCP Use-After-Free: CVE-2026-98432 / CVSS 9.8
Anthropic researcher reported a PoC for remote root access on Linux servers with multipath TCP listeners.
The Linux kernel has a use-after-free vulnerability in IPv4 TCP handshake handling, CVE-2026-98432. The kernel CNA scores it Critical with CVSS 3.1 9.8. Fixed releases include 5.10.272, 5.15.223, 6.1.190, 6.6.159, 6.12.113, 6.18.56, 7.2.10 and 7.3. As of late October 2026, Ubuntu lists all releases as vulnerable and Red Hat lists RHEL 8, 9 and 10 as affected with no fix. The issue occurs before any application code runs and could lead to kernel heap disclosure or DoS.
Unconfirmed: Whether the PoC allows arbitrary command execution as root remains unconfirmed since the exploit was not publicly released.
- CVSS 3.1 9.8 Critical, AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Fixed in Linux 5.10.272, 5.15.223, 6.1.190, 6.6.159, 6.12.113, 6.18.56, 7.2.10 and 7.3
- PoC exploit developed by Anthropic's Claude model but not publicly released
- Ubuntu and Red Hat still list some versions as vulnerable as of October 29, 2026
| Product | Affected | Fixed in |
|---|---|---|
| Red Hat RHEL | 8, 9, 10 | — |
| Ubuntu Linux kernel | all releases | — |
| SUSE SLES | 15 SP4, SP5, SP6 | 16.0 |
| Amazon Linux | 2, 2023 | 2023 kernel versions |
- 1.Check Ubuntu and Red Hat security trackers
- 2.Review distribution kernel updates
- CVEs
- CVE-2026-98432
- Products
- Linux kernel
- Organizations
- Anthropic
- AI models
- Claude
Vulnerabilities mentioned
All| CVE | Vulnerability | CVSS | EPSS | Signals | Published |
|---|---|---|---|---|---|
| CVE-2026-98432 | Use-after-free in Linux kernel IPv4 TCP options | 9.8 | <1% | PoC ×25 |
From the original article
10 min read at atlasum.netLinux's stable kernels shipped a fix on October 11 and 15, 2026 for CVE-2026-98432 , a use-after-free in the IPv4 TCP handshake that a remote, unauthenticated peer can reach. The kernel's own CVE Numbering Authority (CNA) scores it CVSS 3. 1 9.
By oger · atlasum.net
A short excerpt; the article and its images belong to the publisher. Summary, key facts and assessment above are AI-written from the article and can be wrong.