VulnerabilityPublished 28 Oct 2026

CVE-2026-99138: Linux kernel · TCP_CC_INFO

Source GCVE Database

Authoritative record:CVE-2026-99138

Not known to be exploited · fixed in 86814e5370068ec2bf0caa6e6d55c3e5bfc6c324 : patch Linux kernel soon.

Data as of 28 Oct 2026, 14:02 UTC

Severity

High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

Patch: Available – fixed in 86814e5370068ec2bf0caa6e6d55c3e5bfc6c324, 385e474086c2e7e29e2dded690be40dc273e20ee, 39aa489e85752f9de214edb0f85e4d578e57af29

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.

ghsa-xjqr-qmx4-h4w3

What to do

Upgrade Linux kernel to 86814e5370068ec2bf0caa6e6d55c3e5bfc6c324, 385e474086c2e7e29e2dded690be40dc273e20ee or 39aa489e85752f9de214edb0f85e4d578e57af29.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 0baf26b0fcd74bbfcef53c5d5e8bad2b99c8d0d2, < 86814e5370068ec2bf0caa6e6d55c3e5bfc6c324	Fixed in 86814e5370068ec2bf0caa6e6d55c3e5bfc6c324
LinuxLinux	Affected ≥ 0baf26b0fcd74bbfcef53c5d5e8bad2b99c8d0d2, < 385e474086c2e7e29e2dded690be40dc273e20ee	Fixed in 385e474086c2e7e29e2dded690be40dc273e20ee
LinuxLinux	Affected ≥ 0baf26b0fcd74bbfcef53c5d5e8bad2b99c8d0d2, < 39aa489e85752f9de214edb0f85e4d578e57af29	Fixed in 39aa489e85752f9de214edb0f85e4d578e57af29
LinuxLinux	Affected =5.6	Fixed in–
Linuxlinux/kernel`pkg:deb/linux/kernel`Other threats	Affected =5.6	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix for this vulnerability has been implemented in the Linux kernel by adding proper synchronization (rcu_read_lock/unlock) and safe pointer loading (READ_ONCE) in the affected code. Users should apply the official kernel updates that include this fix once available. No alternative mitigations are indicated.

Description

A use-after-free vulnerability in the Linux kernel's TCP implementation (do_tcp_getsockopt with TCP_CC_INFO) was fixed. The flaw involved dereferencing a stale pointer to congestion control operations without proper synchronization, potentially causing kernel memory corruption.

Impact

This vulnerability can lead to kernel memory corruption due to use-after-free, which may cause system instability or crashes. There is no indication of confirmed exploitation in the wild or direct privilege escalation from the provided data.

Summary

The vulnerability in the Linux kernel occurs in the function do_tcp_getsockopt() when handling TCP_CC_INFO socket options. The function reads the icsk->icsk_ca_ops pointer and calls its get_info function without holding the rcu_read_lock(), leading to a use-after-free condition if the congestion control operations pointer is dynamically freed concurrently. This flaw can cause a kernel slab-use-after-free error, as demonstrated by KASAN detection. The fix involves wrapping the ca_ops pointer load and get_info call within rcu_read_lock()/rcu_read_unlock() and using READ_ONCE() to safely load the pointer, preventing concurrent use-after-free.

References

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