VulnerabilityPublished 28 Oct 2026

CVE-2026-99139: Linux kernel · TCP_CONGESTION

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in c1804ef016392dd91267d2207ee43b1de34302ca : update Linux kernel when convenient.

Data as of 28 Oct 2026, 10:58 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

Patch: Available – fixed in c1804ef016392dd91267d2207ee43b1de34302ca, a8e45471afa230c1431c26c8e99ec24377e3b514, 5271b79b7ad68dcb222e893773f92bdabf7750f3

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Linux kernel to c1804ef016392dd91267d2207ee43b1de34302ca, a8e45471afa230c1431c26c8e99ec24377e3b514 or 5271b79b7ad68dcb222e893773f92bdabf7750f3.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 0baf26b0fcd74bbfcef53c5d5e8bad2b99c8d0d2, < c1804ef016392dd91267d2207ee43b1de34302ca	Fixed in c1804ef016392dd91267d2207ee43b1de34302ca
LinuxLinux	Affected ≥ 0baf26b0fcd74bbfcef53c5d5e8bad2b99c8d0d2, < a8e45471afa230c1431c26c8e99ec24377e3b514	Fixed in a8e45471afa230c1431c26c8e99ec24377e3b514
LinuxLinux	Affected ≥ 0baf26b0fcd74bbfcef53c5d5e8bad2b99c8d0d2, < 5271b79b7ad68dcb222e893773f92bdabf7750f3	Fixed in 5271b79b7ad68dcb222e893773f92bdabf7750f3
LinuxLinux	Affected =5.6	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION) do_tcp_getsockopt() reads icsk->icsk_ca_ops->name without holding rcu_read_lock(). Since commit 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf"), icsk_ca_ops can point to dynamically allocated BPF struct_ops memory that may be freed concurrently via setsockopt(TCP_CONGESTION), leading to a use-after-free. BUG: KASAN: slab-use-after-free in _copy_to_user+0x37/0x60 Read of size 16 at addr ffff888013505260 by task exploit/149 _copy_to_user+0x37/0x60 do_tcp_getsockopt+0x158a/0x2460 (net/ipv4/tcp.c:4585) tcp_getsockopt+0x91/0xf0 __sys_getsockopt+0xf7/0x170 Fix this by holding rcu_read_lock() around the ca_ops->name access, using READ_ONCE() to load icsk_ca_ops, and copying the name to a stack buffer before releasing the lock. Also annotate the relevant icsk_ca_ops stores with WRITE_ONCE() to fix the accompanying KCSAN data-race issue.

References

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