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LSN-0121-1: Kernel Live Patch Security Notice

unknownknown exploitedpublic exploitCVE-2026-31431CVE-2026-43406CVE-2026-47333
Actively exploited. At least one CVE in this advisory is listed in the CISA Known Exploited Vulnerabilities catalog — exploitation has been observed in the wild. Treat remediation as urgent.
In the Linux kernel, the following vulnerability has been resolved: ksmbd: ipc: fix use-after-free in ipc_msg_send_request ipc_msg_send_request() waits for a generic netlink reply using an ipc_msg_table_entry on the stack. In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free of share_conf in compound request smb2_get_ksmbd_tcon() reuses work->tcon in compound requests without validating tcon->t_state. In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() In DecodeQ931(), the UserUserIE code path reads a 16-bit length from the packet, then decrements it by 1 to skip the protocol discriminator byte before passing it to DecodeH323_UserInformation(). In the Linux kernel, the following vulnerability has been resolved: nfsd: fix heap overflow in NFSv4.0 LOCK replay cache The NFSv4.0 replay cache uses a fixed 112-byte inline buffer (rp_ibuf. In the Linux kernel, the following vulnerability has been resolved: media: dvb-net: fix OOB access in ULE extension header tables The ule_mandatory_ext_handlers. It was discovered that the Linux kernel algif_aead module did not properly handle in-place cryptographic operations. This flaw is known as Copy Fail. A local attacker could use this to escalate privileges, or possibly escape a container.)(CVE-2026-31431) In the Linux kernel, the following vulnerability has been resolved: ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len() After this commit (e2b76ab8b5c9 'ksmbd: add support for read compound'), response buffer management was changed to use dynamic iov array. In the Linux kernel, the following vulnerability has been resolved: usbip: validate number_of_packets in usbip_pack_ret_submit() When a USB/IP client receives a RET_SUBMIT response, usbip_pack_ret_submit() unconditionally overwrites urb->number_of_packets from the network PDU. This value is subsequently used as the loop boun

CSIRTS triage

What
Linux kernel contains use-after-free and buffer overflow vulnerabilities in ksmbd IPC, netfilter, and NFSv4.0 subsystems.
Who is affected
Linux systems running affected kernel versions, particularly those with ksmbd, netfilter, and NFSv4 enabled.
Urgency
Critical; actively exploited vulnerabilities affecting core kernel subsystems.
Action
Apply Linux kernel security updates from your distribution immediately; apply live patches if available.

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
2026-08-27
Exploitation
Observed in the wild (CISA KEV)

Original advisory: https://ubuntu.com/security/notices/LSN-0121-1

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.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-31431coverage & exploitation statusNVD · CVE.org
CVE-2026-43406coverage & exploitation statusNVD · CVE.org
CVE-2026-47333coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

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

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