Quick answers
- Is CVE-2026-99138 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-99138 being exploited in the wild.
- How severe is CVE-2026-99138?
- Informational severity, published 28 October 2026.
- Which products and versions are affected?
- Linux kernel 5.18 and later (vulnerable since BPF tcp_congestion_ops support; patched in 6.11+.
- Is there a fix for CVE-2026-99138?
- Yes: fixed in Linux kernel 6.11 and later stable releases. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-99138 attacked?
- It is attacked over the network or with local access, in an operating system.
- Am I affected by CVE-2026-99138?
- Check whether you run Linux kernel at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: Linux kernel 6.11 and later stable releases
Technical details
do_tcp_getsockopt() dereferences a TCP congestion control operations pointer (icsk_ca_ops) without RCU synchronization. When BPF struct_ops congestion control is active, the underlying memory can be freed concurrently by another CPU, causing a use-after-free. The vulnerability allows an unprivileged attacker with network access or local ability to call getsockopt(TCP_CC_INFO) to trigger a KASAN slab-use-after-free condition.
Affected products
- Linux kernel 5.18 and later (vulnerable since BPF tcp_congestion_ops support; patched in 6.11+
Timeline
- 2026-08-28: disclosed
- 2026-08-28: patched