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Vulnerability · Published Apr 24, 2026 · Assigned by Linux

CVE-2026-31609smb: client: avoid double-free in smbd_free_send_io() after smbd_send_batch_flush()

Critical 9.8

In plain English

A critical-severity double free in Linux from Linux. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.8Critical
Exploit odds (30 days)0.5%top 60.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

In the Linux kernel, the following vulnerability has been resolved: smb: client: avoid double-free in smbd_free_send_io() after smbd_send_batch_flush() smbd_send_batch_flush() already calls smbd_free_send_io(), so we should not call it again after smbd_post_send() moved it to the batch list.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:14linux6.19.14-1DEBIAN-CVE-2026-31609
Ubuntu:26.04:LTSlinux7.0.0-27.27UBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux7.0.0-27.27USN-8488-1
Ubuntu:22.04:LTSlinux-allwinner-5.19no fix listedUBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-aws7.0.0-1008.8USN-8488-1
Ubuntu:26.04:LTSlinux-aws7.0.0-1008.8UBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-aws-5.19no fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-aws-6.14no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-aws-6.2no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-aws-6.5no fix listedUBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-azure7.0.0-1010.10UBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-azure7.0.0-1010.10USN-8603-1
Ubuntu:22.04:LTSlinux-azure-5.19no fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-azure-6.11no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-azure-6.2no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-azure-6.5no fix listedUBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-azure-fde7.0.0-1009.9USN-8603-1
Ubuntu:26.04:LTSlinux-azure-fde7.0.0-1009.9UBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-azure-fde-5.19no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-azure-fde-6.2no fix listedUBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-gcp7.0.0-1007.7USN-8488-1
Ubuntu:26.04:LTSlinux-gcp7.0.0-1007.7UBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-gcp-5.19no fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-gcp-6.11no fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-gcp-6.14no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-gcp-6.2no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-gcp-6.5no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-hwe-5.19no fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-hwe-6.11no fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-hwe-6.14no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-hwe-6.2no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-hwe-6.5no fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-hwe-7.07.0.0-28.28~24.04.1UBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-hwe-7.07.0.0-28.28~24.04.1USN-8569-1
Ubuntu:26.04:LTSlinux-ibm7.0.0-1009.9USN-8488-1
Ubuntu:26.04:LTSlinux-ibm7.0.0-1009.9UBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-intel-iot-realtimeno fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-lowlatency-hwe-5.19no fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-lowlatency-hwe-6.11no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.2no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.5no fix listedUBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-nvidia7.0.0-1013.13UBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-nvidia7.0.0-1013.13USN-8507-1
Ubuntu:24.04:LTSlinux-nvidia-6.11no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-nvidia-6.2no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-nvidia-6.5no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-oem-5.17no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-oem-6.0no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-oem-6.1no fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-oem-6.11no fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-oem-6.14no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-oem-6.5no fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-oem-6.8no fix listedUBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-oracle7.0.0-1007.7USN-8488-1
Ubuntu:26.04:LTSlinux-oracle7.0.0-1007.7UBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-oracle-6.14no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-oracle-6.5no fix listedUBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-raspi7.0.0-1014.14UBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-raspi7.0.0-1014.14USN-8488-2
Ubuntu:24.04:LTSlinux-raspi-realtimeno fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-realtime7.0.0-27.27.1UBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-realtime7.0.0-27.27.1USN-8488-1
Ubuntu:22.04:LTSlinux-riscvno fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-riscvno fix listedUBUNTU-CVE-2026-31609
Ubuntu:26.04:LTSlinux-riscv7.0.0-27.27.1UBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-riscv-5.19no fix listedUBUNTU-CVE-2026-31609
Ubuntu:24.04:LTSlinux-riscv-6.14no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-riscv-6.5no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-starfive-5.19no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-starfive-6.2no fix listedUBUNTU-CVE-2026-31609
Ubuntu:22.04:LTSlinux-starfive-6.5no fix listedUBUNTU-CVE-2026-31609

Affected products (as reported)

VendorProductVersions
Linux Linux cca0526ef2344cab6944d7f441fc24e152da031b – before a9940dcbe5cb92482c04efc7341039ddf7dbf60737b5c06956183b65e6808b509cf637632016cdf7 – before 22b7c1c619d808aec4cad3dc42103345e370d10721538121efe6c8c5b51c742fa02cbe820bc48714 – before f9a162c2bbcd0ac85bd07c5b37cf20286048b65c21538121efe6c8c5b51c742fa02cbe820bc48714 – before 27b7c3e916218b5eb2ee350211140e961bfc49be6.18.11 – before 6.18.246.19.1 – before 6.19.14
Linux Linux 7.0

Weakness: CWE-415 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References