USN-8635-1: Linux kernel (Azure) vulnerabilities

unknownpublic exploitCVE-2020-24588 CVE-2025-27558 CVE-2026-43503 CVE-2021-47202 CVE-2021-47354 CVE-2021-47378

Siebe Devroe, Héloïse Gollier, and Mathy Vanhoef discovered that the WiFi implementation in the Linux kernel did not properly handle aggregated frames in mesh networks, due to an incorrect fix for CVE-2020-24588. A physically proximate attacker could use this issue to inject packets. (CVE-2025-27558) 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: - x86 architecture; - Cryptographic API; - GPU drivers; - InfiniBand drivers; - Media drivers; - NVIDIA Tegra memory controller driver; - Network drivers; - STMicroelectronics network drivers; - NVME drivers; - SCSI subsystem; - Thermal drivers; - USB over IP driver; - Ext4 file system; - Network file system (NFS) server daemon; - SMB network file system; - IPv4 networking; - Network traffic control; - TCP network protocol; - Tracing infrastructure; - Locking primitives; - B.A.T.M.A.N. meshing protocol; - Ethernet bridge; - Ceph Core library; - DCCP (Datagram Congestion Control Protocol); - IPv6 networking; - Multipath TCP; - Netfilter; - RxRPC session sockets; - SCTP protocol; - SMC sockets; - X.25 network layer; (CVE-2021-47202, CVE-2021-47354, CVE-2021-47378, CVE-2024-38612, CVE-2024-56643, CVE-2026-23272, CVE-2026-23455, CVE-2026-31402, CVE-2026-31405, CVE-2026-31414, CVE-2026-31448, CVE-2026-31607, CVE-2026-31637, CVE-2026-31649, CVE-2026-31657, CVE-2026-31659, CVE-2026-31668, CVE-2026-31682, CVE-2026-31685, CVE-2026-43011, CVE-2026-43037, CVE-2026-43038, CVE-2026-43198, CVE-2026-43383, CVE-2026-43407, CVE-2026-43414, CVE-2026-43493, CVE-2026-43499, CVE-2026-45988, CVE-2026-46043, CVE-2026-46119, CVE-2026-46243, CVE-202

CSIRTS triage

vendor: Linux product: Linux kernel Remote code execution Privilege escalation Information disclosure Denial of service Memory corruption

What: WiFi mesh frame injection flaw (CVE-2025-27558) and XFRM ESP-in-TCP privilege escalation (CVE-2026-43503) plus multiple other kernel subsystem flaws.
Who is affected: Azure deployments and systems running affected Linux kernel versions with WiFi mesh or XFRM networking in use.
Urgency: High; CVE-2026-43503 allows local privilege escalation and container escape, actively exploitable by local attackers.
Action: Apply kernel security update USN-8635-1 from Ubuntu security repositories immediately.

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: 2026-08-12
Exploitation: Not in CISA KEV at last sync

Original advisory: https://ubuntu.com/security/notices/USN-8635-1

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.

Moderate exploitation riskCVE-2020-245883.5% 30-day exploitation probability. Patch within normal cadence, watch for KEV listing. Riskier than 88% of all EPSS-scored CVEs.
Low exploitation riskCVE-2025-275580.29% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 21% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-435030.34% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 27% of all EPSS-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 EPSS-scored CVEs.
Low exploitation riskCVE-2021-473540.73% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 51% of all EPSS-scored CVEs.
Moderate exploitation riskCVE-2021-473781.2% 30-day exploitation probability. Patch within normal cadence, watch for KEV listing. Riskier than 65% of all EPSS-scored CVEs.
Low exploitation riskCVE-2024-386120.68% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 49% of all EPSS-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 EPSS-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 EPSS-scored CVEs.
Moderate exploitation riskCVE-2026-234551.3% 30-day exploitation probability. Patch within normal cadence, watch for KEV listing. Riskier than 69% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2020-24588	coverage & exploitation status	NVD · CVE.org
CVE-2025-27558	coverage & exploitation status	NVD · CVE.org
CVE-2026-43503	coverage & exploitation status	NVD · CVE.org
CVE-2021-47202	coverage & exploitation status	NVD · CVE.org
CVE-2021-47354	coverage & exploitation status	NVD · CVE.org
CVE-2021-47378	coverage & exploitation status	NVD · CVE.org
CVE-2024-38612	coverage & exploitation status	NVD · CVE.org
CVE-2024-56643	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-2026-31402	coverage & exploitation status	NVD · CVE.org
CVE-2026-31405	coverage & exploitation status	NVD · CVE.org
CVE-2026-31414	coverage & exploitation status	NVD · CVE.org
CVE-2026-31448	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-2026-31657	coverage & exploitation status	NVD · CVE.org
CVE-2026-31659	coverage & exploitation status	NVD · CVE.org
CVE-2026-31668	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-2026-43037	coverage & exploitation status	NVD · CVE.org
CVE-2026-43038	coverage & exploitation status	NVD · CVE.org
CVE-2026-43198	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-2026-43493	coverage & exploitation status	NVD · CVE.org
CVE-2026-43499	coverage & exploitation status	NVD · CVE.org
CVE-2026-45988	coverage & exploitation status	NVD · CVE.org
CVE-2026-46043	coverage & exploitation status	NVD · CVE.org
CVE-2026-46119	coverage & exploitation status	NVD · CVE.org
CVE-2026-46243	coverage & exploitation status	NVD · CVE.org
CVE-2026-46266	coverage & exploitation status	NVD · CVE.org
CVE-2026-46331	coverage & exploitation status	NVD · CVE.org
CVE-2026-52924	coverage & exploitation status	NVD · CVE.org
CVE-2026-52931	coverage & exploitation status	NVD · CVE.org
CVE-2026-52955	coverage & exploitation status	NVD · CVE.org
CVE-2026-52982	coverage & exploitation status	NVD · CVE.org
CVE-2026-52986	coverage & exploitation status	NVD · CVE.org
CVE-2026-53002	coverage & exploitation status	NVD · CVE.org
CVE-2026-53006	coverage & exploitation status	NVD · CVE.org
CVE-2026-53045	coverage & exploitation status	NVD · CVE.org
CVE-2026-53088	coverage & exploitation status	NVD · CVE.org
CVE-2026-53176	coverage & exploitation status	NVD · CVE.org
CVE-2026-53225	coverage & exploitation status	NVD · CVE.org

+2 more CVEs referenced in this advisory.

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