USN-8617-1: Linux kernel (KVM) vulnerabilities

unknownCVE-2026-43503 CVE-2026-23272 CVE-2026-23455 CVE-2026-31418 CVE-2026-31607 CVE-2026-31637

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: - InfiniBand drivers; - STMicroelectronics network drivers; - SCSI subsystem; - USB over IP driver; - SMB network file system; - Tracing infrastructure; - B.A.T.M.A.N. meshing protocol; - Ethernet bridge; - Ceph Core library; - IPv4 networking; - IPv6 networking; - Netfilter; - RxRPC session sockets; - X.25 network layer; (CVE-2026-23272, CVE-2026-23455, CVE-2026-31418, CVE-2026-31607, CVE-2026-31637, CVE-2026-31649, CVE-2026-31659, CVE-2026-31682, CVE-2026-31685, CVE-2026-43011, CVE-2026-43038, CVE-2026-43117, CVE-2026-43383, CVE-2026-43407, CVE-2026-43414, CVE-2026-46043, CVE-2026-46243)

CSIRTS triage

vendor: Linux product: Linux kernel Privilege escalationOther

What: A logic flaw in the Linux kernel could allow local attackers to escalate privileges or escape a container.
Who is affected: Users of the Linux kernel are affected.
Urgency: Remediation is necessary, but severity is currently unknown.
Action: Update to the latest version of 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: 2026-07-28
Exploitation: Not in CISA KEV at last sync

Original advisory: https://ubuntu.com/security/notices/USN-8617-1

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-2026-232720.12% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% 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-2026-314180.12% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% 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-2026-316490.46% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 38% 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.
Low exploitation riskCVE-2026-316820.48% 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-2026-316850.34% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 26% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-43503	coverage & exploitation status	NVD · CVE.org
CVE-2026-23272	coverage & exploitation status	NVD · CVE.org
CVE-2026-23455	coverage & exploitation status	NVD · CVE.org
CVE-2026-31418	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-2026-31649	coverage & exploitation status	NVD · CVE.org
CVE-2026-31659	coverage & exploitation status	NVD · CVE.org
CVE-2026-31682	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-2026-43038	coverage & exploitation status	NVD · CVE.org
CVE-2026-43117	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-2026-46043	coverage & exploitation status	NVD · CVE.org
CVE-2026-46243	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

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unknownUSN-8615-2: Linux kernel (Raspberry Pi) vulnerabilitiesubuntu
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highUSN-8619-1: Linux kernel (HWE) vulnerabilitiesubuntu
unknownUSN-8616-1: Linux kernel (IBM) vulnerabilitiesubuntu