LSN-0121-1: Kernel Live Patch Security Notice
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
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.
- Exploitation confirmedCVE-2026-31431Already exploited in the wild (CISA KEV) — the prediction phase is over. Patch now. Riskier than 99.9% of all EPSS-scored CVEs.
- Low exploitation riskCVE-2026-434060.50% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 41% of all EPSS-scored CVEs.
- Low exploitation riskCVE-2026-473330.11% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 1% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-31431 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-43406 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-47333 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
- unknownexploitedNCSC-2026-0346 [1.01] [M/H] Kwetsbaarheden verholpen in Siemens productenncsc-nl
- highexploited[UPDATE] [hoch] Linux Kernel: Mehrere Schwachstellencert-bund
- unknownexploitedMultiples vulnérabilités dans les produits Siemens (08 septembre 2026)cert-fr-avis
- unknownexploitedCVE-2026-31431aws
- unknownexploitedDirty Frag and other issues in Amazon Linux kernelsaws
- unknownexploitedOngoing updates on Copy.fail and variantsaws
- unknownexploitedMultiple vulnerabilities in SUSE Linux kernel (August 14, 2026)cert-fr-avis
- highexploited[UPDATE] [high] Linux Kernel (Dirty Frag): Multiple vulnerabilities allow gaining administrator rightscert-bund
- highexploitedCVE-2026-31431: crypto: algif_aead - Revert to operating out-of-placemsrc
- high[UPDATE] [high] IBM QRadar SIEM: Multiple vulnerabilitiescert-bund
- unknownexploitedSiemens SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFPcisa
- high[NEW] [high] Oracle Communications: Multiple vulnerabilitiescert-bund
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