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CVE Record

CVE-2026-43198: tcp: fix potential race in tcp_v6_syn_recv_sock()

In the Linux kernel, the following vulnerability has been resolved: tcp: fix potential race in tcp_v6_syn_recv_sock() Code in tcp_v6_syn_recv_sock() after the call to tcp_v4_syn_recv_sock() is done too late. After tcp_v4_syn_recv_sock(), the child socket is already visible from TCP ehash table and other cpus might use it. Since newinet->pinet6 is still pointing to the listener ipv6_pinfo bad things can happen as syzbot found. Move the problematic code in tcp_v6_mapped_child_init() and call this new helper from tcp_v4_syn_recv_sock() before the ehash insertion. This allows the removal of one tcp_sync_mss(), since tcp_v4_syn_recv_sock() will call it with the correct context.

CriticalCVSS 9.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-43198 is a critical Linux kernel networking flaw in TCP connection setup. A race condition can leave a newly accepted socket visible to other CPUs before its IPv6 state is correctly initialized. The published scoring treats this as remotely reachable with high confidentiality, integrity, and availability impact.

Executive priority

Treat this as urgent for externally reachable Linux infrastructure. The technical trigger is kernel-level and network-facing, so successful exploitation could affect host stability or security boundaries. Patch based on vendor guidance and verify rebooted kernels.

Technical view

The flaw is in tcp_v6_syn_recv_sock(). After tcp_v4_syn_recv_sock(), the child socket is already in the TCP ehash table, while newinet->pinet6 may still reference listener IPv6 state. The kernel fix moves initialization into tcp_v6_mapped_child_init() before ehash insertion.

Likely exposure

Exposure is most relevant to systems running affected Linux kernels that accept TCP connections, especially IPv6 or IPv4-mapped IPv6 listener paths. The bundle identifies Linux kernel versions and Red Hat advisories, but product-level status must be confirmed against each vendor kernel package.

Exploitation context

The source bundle marks KEV as false and provides no cited evidence of active exploitation. The issue was found by syzbot, and the CVSS vector indicates remote, unauthenticated, low-complexity reachability, but the bundle does not include public exploit details.

Researcher notes

Evidence supports a race in TCP child socket initialization before ehash insertion. The precise vulnerable version ranges in the bundle are broad and vendor packaging may differ, so validation should rely on kernel commits, distro advisories, and package backports.

Mitigation direction

  • Inventory Linux kernel versions across exposed systems.
  • Apply vendor kernel updates or stable fixes for CVE-2026-43198.
  • Prioritize internet-facing TCP services and shared hosting nodes.
  • Check Red Hat advisories for affected package status.
  • If updates are unavailable, follow vendor guidance and reduce unnecessary TCP exposure.

Validation and detection

  • Confirm the running kernel after reboot, not only the installed package.
  • Compare kernel packages against vendor CVE or errata status.
  • Check whether exposed services accept TCP over IPv6 paths.
  • Track Red Hat VEX and RHSA records for environment-specific status.
  • Document exceptions where vendor status remains unclear.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2026-43198 mapping review

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
1ADP providers
20Source links

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.8CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Linux
7CVSS 3.1HighCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H15.9redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

9.8Critical
CVSS 3.1 vector shape for CVE-2026-43198Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Reported to Red Hat.

  3. ADP timelineredhat-SADP

    Made public.

  4. CVE publishedCVE Program

    The CVE record was published.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

redhat-SADPkernel: tcp: fix potential race in tcp_v6_syn_recv_sock()
other:Red Hat severity ratingcvssV3_1
  • 2026-05-06T00:00:00.000Z: Reported to Red Hat.
  • 2026-05-06T00:00:00.000Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2unaffected
LinuxLinux2.6.12, 0, 6.18.16, 6.19.6, 7.0affected
Weakness

CWE details

CWE-821

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Incorrect Synchronization

Incorrect Synchronization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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