Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-43198 is a critical-severity concurrent execution using shared resource with improper synchronization vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions aef4a9ae95d1bc4f7897065011e6261026719aeb, dad1fe7db6c6519138430ac8f5e589c18f83bfc9, a7e761ba55efaa9c49e0afdd304bb78167af3429 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.3% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to aef4a9ae95d1bc4f7897065011e6261026719aeb or dad1fe7db6c6519138430ac8f5e589c18f83bfc9 or a7e761ba55efaa9c49e0afdd304bb78167af3429 or cd644e6dc72eec8d9d988717ea1c54f8668ded69, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.18.16 or 6.19.6, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, aef4a9ae95d1bc4f7897065011e6261026719aeb; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, dad1fe7db6c6519138430ac8f5e589c18f83bfc9; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, a7e761ba55efaa9c49e0afdd304bb78167af3429; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, cd644e6dc72eec8d9d988717ea1c54f8668ded69; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 9ed654e340f4c73bc6f0af2fbc90ac293e645ce0; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, fe89b2f05b854847784f91127319172945c1fadd; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 7178e2a8027423b2af17ab95df73a749a5b72e5b; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 858d2a4f67ff69e645a43487ef7ea7f28f06deae; and 1 more ranges | aef4a9ae95d1bc4f7897065011e6261026719aeb, dad1fe7db6c6519138430ac8f5e589c18f83bfc9, a7e761ba55efaa9c49e0afdd304bb78167af3429, cd644e6dc72eec8d9d988717ea1c54f8668ded69, 9ed654e340f4c73bc6f0af2fbc90ac293e645ce0, fe89b2f05b854847784f91127319172945c1fadd |
| Red Hat | Red Hat Enterprise Linux 10 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 10.0 Extended Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 7 Extended Lifecycle Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.8 Telecommunications Update Service | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9.6 Extended Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 6 | Not specified in the record | Not stated |
| Linux | Linux Kernel | 2.6.12.1 up to, but not including, 6.18.16; 6.19 up to, but not including, 6.19.6; 2.6.12; 7.0 | 6.18.16, 6.19.6 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | CNA |
| CVSS 3.1 | 7.0 | High | CNA |
Official description
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
How developers prevent this class of flaw
- In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
- Use thread-safe capabilities such as the data access abstraction in Spring.
- Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
- git.kernel.org/stable/c/9ed654e340f4c73bc6f0af2fbc90ac293e645ce0
- git.kernel.org/stable/c/a7e761ba55efaa9c49e0afdd304bb78167af3429
- git.kernel.org/stable/c/aef4a9ae95d1bc4f7897065011e6261026719aeb
- git.kernel.org/stable/c/cd644e6dc72eec8d9d988717ea1c54f8668ded69
- git.kernel.org/stable/c/dad1fe7db6c6519138430ac8f5e589c18f83bfc9
- access.redhat.com/errata/RHSA-2026:30129
- access.redhat.com/errata/RHSA-2026:33215
- access.redhat.com/errata/RHSA-2026:33285
- access.redhat.com/errata/RHSA-2026:34094
- access.redhat.com/errata/RHSA-2026:34443
- access.redhat.com/errata/RHSA-2026:35863
- access.redhat.com/errata/RHSA-2026:35894
- access.redhat.com/errata/RHSA-2026:35896
- access.redhat.com/errata/RHSA-2026:35904
- access.redhat.com/errata/RHSA-2026:36073
Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities
- 7.5 High severity
- 8.8 High severity
- 7.8 High severity
- 7.5 High severity
- 7.8 High severity
- 7.8 High severity
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