USN-8548-1: Linux kernel vulnerabilities

unknownCVE-2026-43503 CVE-2021-47117 CVE-2021-47202 CVE-2023-52646 CVE-2024-56643 CVE-2026-23455

It was discovered that a logic flaw existed in the XFRM ESP-in-TCP subsystem in the Linux kernel when handling socket buffer fragments. This flaw is known as Fragnesia. A local attacker could use this to escalate privileges, or possibly escape a container. (CVE-2026-43503) Several security issues were discovered in the Linux kernel. An attacker could possibly use these to compromise the system. This update corrects flaws in the following subsystems: - SCSI subsystem; - Thermal drivers; - USB over IP driver; - File systems infrastructure; - Ext4 file system; - Network file system (NFS) server daemon; - SMB network file system; - Tracing infrastructure; - B.A.T.M.A.N. meshing protocol; - Ceph Core library; - DCCP (Datagram Congestion Control Protocol); - IPv4 networking; - IPv6 networking; - Netfilter; - RxRPC session sockets; - X.25 network layer; (CVE-2021-47117, CVE-2021-47202, CVE-2023-52646, CVE-2024-56643, CVE-2026-23455, CVE-2026-31402, CVE-2026-31607, CVE-2026-31637, CVE-2026-31659, CVE-2026-31685, CVE-2026-43011, CVE-2026-43037, CVE-2026-43038, CVE-2026-43383, CVE-2026-43407, CVE-2026-43414, CVE-2026-45988, CVE-2026-46119, CVE-2026-46243)

CSIRTS triage

vendor: Linux product: Linux kernel Privilege escalationOther

What: A logic flaw in the XFRM ESP-in-TCP subsystem could allow local privilege escalation.
Who is affected: All deployments using the affected Linux kernel versions.
Urgency: Remediation is urgent due to the potential for local privilege escalation and system compromise.
Action: Apply the latest security updates for the Linux kernel.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Ubuntu Security Notices (INTL · vendor-psirt · site)
Severity: unknown
Published: 2026-07-15
Exploitation: Not in CISA KEV at last sync

Original advisory: https://ubuntu.com/security/notices/USN-8548-1

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-435030.34% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 26% of all scored CVEs.
Low exploitation riskCVE-2021-471170.24% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 15% of all scored CVEs.
Low exploitation riskCVE-2021-472020.24% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 15% of all scored CVEs.
Low exploitation riskCVE-2023-526460.24% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 15% of all scored CVEs.
Low exploitation riskCVE-2024-566430.23% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 14% of all scored CVEs.
Moderate exploitation riskCVE-2026-234551.3% 30-day exploitation probability. Patch within normal cadence, watch for KEV listing. Riskier than 68% of all scored CVEs.
Low exploitation riskCVE-2026-314020.49% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 39% of all scored CVEs.
Low exploitation riskCVE-2026-316070.31% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 24% of all scored CVEs.
Low exploitation riskCVE-2026-316370.51% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 41% of all scored CVEs.
Low exploitation riskCVE-2026-316590.40% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 33% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-43503	coverage & exploitation status	NVD · CVE.org
CVE-2021-47117	coverage & exploitation status	NVD · CVE.org
CVE-2021-47202	coverage & exploitation status	NVD · CVE.org
CVE-2023-52646	coverage & exploitation status	NVD · CVE.org
CVE-2024-56643	coverage & exploitation status	NVD · CVE.org
CVE-2026-23455	coverage & exploitation status	NVD · CVE.org
CVE-2026-31402	coverage & exploitation status	NVD · CVE.org
CVE-2026-31607	coverage & exploitation status	NVD · CVE.org
CVE-2026-31637	coverage & exploitation status	NVD · CVE.org
CVE-2026-31659	coverage & exploitation status	NVD · CVE.org
CVE-2026-31685	coverage & exploitation status	NVD · CVE.org
CVE-2026-43011	coverage & exploitation status	NVD · CVE.org
CVE-2026-43037	coverage & exploitation status	NVD · CVE.org
CVE-2026-43038	coverage & exploitation status	NVD · CVE.org
CVE-2026-43383	coverage & exploitation status	NVD · CVE.org
CVE-2026-43407	coverage & exploitation status	NVD · CVE.org
CVE-2026-43414	coverage & exploitation status	NVD · CVE.org
CVE-2026-45988	coverage & exploitation status	NVD · CVE.org
CVE-2026-46119	coverage & exploitation status	NVD · CVE.org
CVE-2026-46243	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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