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Linux Kernel IB/isert: Use-after-free during iSER connection teardown

CVE-2026-98357High 8.1

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Summary

A race condition in the Linux kernel iSER target driver (IB/isert) allows a use-after-free. Deferred control PDU completions can run after the connection has been freed during teardown. An attacker who can reach an iSER target over RDMA could potentially read or corrupt kernel memory, which may lead to a crash or code execution. Exploitation requires high complexity and timing, and the target should not be exposed to untrusted networks.

Affected

  • Linux kernel with the IB/isert driver (iSER target), from 3.10 up to the fixed versions listed below, according to the CNA record. Exact ranges per branch should be verified against the stable commits.

Fixed in

  • 5.10.271
  • 5.15.222
  • 6.1.189
  • 6.6.158
  • 6.12.112
  • 6.18.54
  • 7.2.8
  • Later kernel versions of these branches also contain the fix.

Workaround

  • No vendor workaround known.
  • On hosts that do not run an iSER target, ensure the isert kernel module is not loaded.

Exploitation

  • No active exploitation known.
  • No public exploit or proof of concept located. The crash trace in the report comes from a test kernel with injected delays.

Our recommendation

  • Identify storage servers that run an iSER/iSCSI target over RDMA (check lsmod for isert and your storage inventory).
  • Install the distribution kernel update containing the fix with the next regular maintenance window.
  • Do not expose iSER/iSCSI target services to untrusted networks.
  • Reboot after the kernel update so the fixed code is active.

Public exploits

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 20:48.

Original description (NVD)

In the Linux kernel, the following vulnerability has been resolved: IB/isert: wait for deferred control PDU completions before releasing the connection isert_send_done() hands ISTATE_SEND_TASKMGTRSP, ISTATE_SEND_REJECT and ISTATE_SEND_TEXTRSP completions off to isert_comp_wq and returns. The work item then runs isert_completion_put() -> isert_put_cmd(), which reads isert_conn->conn and takes conn->cmd_lock. Nothing orders that work item against teardown. isert_wait_conn() queues isert_release_work, which frees isert_conn, and iscsit_close_connection() frees the iscsit_conn right after it returns, so the queued work can run against freed memory. Count the deferred control PDU completions per connection and let isert_wait_conn() wait for them before the release work is queued. ISTATE_SEND_LOGOUTRSP is deliberately not counted: that branch runs iscsit_logout_post_handler(), which ends up waiting for conn->conn_wait_comp, and that completion is only sent by iscsit_close_connection() after it has called iscsit_wait_conn(). Waiting for it here would deadlock. Its wait stays the existing isert_wait4logout(). The splat below is from a kernel with tracing printk()s and an msleep(200) injected into isert_do_control_comp() to widen the window: BUG: KASAN: slab-use-after-free in isert_put_cmd+0x53d/0x620 Read of size 8 at addr ffff8881054f1038 by task kworker/u17:1/182 CPU: 0 UID: 0 PID: 182 Comm: kworker/u17:1 Tainted: G B 7.2.0-rc5-TWIDE-gb8babf08acc7 #1 PREEMPT(lazy) Tainted: [B]=BAD_PAGE Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Workqueue: isert_comp_wq isert_do_control_comp Call Trace: <TASK> dump_stack_lvl+0x53/0x70 print_report+0xd0/0x630 ? __pfx__raw_spin_lock_irqsave+0x10/0x10 ? _raw_spin_unlock_irqrestore+0x3e/0x70 ? isert_put_cmd+0x53d/0x620 kasan_report+0xce/0x100 ? isert_put_cmd+0x53d/0x620 isert_put_cmd+0x53d/0x620 ? isert_completion_put+0x305/0x330 ? isert_do_control_comp+0x2ef/0x310 process_one_work+0x633/0x1030 ? assign_work+0x11d/0x370 worker_thread+0x45b/0xd10 ? __pfx_worker_thread+0x10/0x10 ? __pfx_worker_thread+0x10/0x10 kthread+0x2c6/0x3b0 ? recalc_sigpending+0x15c/0x1e0 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x36e/0x5a0 ? __pfx_ret_from_fork+0x10/0x10 ? __switch_to+0x572/0xdd0 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> Allocated by task 48: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 __kasan_kmalloc+0x8f/0xa0 __kmalloc_cache_noprof+0x158/0x370 isert_cma_handler+0x1e3/0x2ae0 cma_cm_event_handler+0x3e/0x240 cma_ib_req_handler+0x17d9/0x4490 cm_process_work+0x41/0x330 cm_work_handler+0x5727/0xc160 process_one_work+0x633/0x1030 worker_thread+0x45b/0xd10 kthread+0x2c6/0x3b0 ret_from_fork+0x36e/0x5a0 ret_from_fork_asm+0x1a/0x30 Freed by task 184: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 kasan_save_free_info+0x3b/0x60 __kasan_slab_free+0x43/0x70 kfree+0x121/0x380 iscsit_close_connection+0x7cf/0x1e60 iscsit_take_action_for_connection_exit+0x1b6/0x360 iscsi_target_tx_thread+0x472/0x690 kthread+0x2c6/0x3b0 ret_from_fork+0x36e/0x5a0 ret_from_fork_asm+0x1a/0x30

NVD references (8)

Sources

The tracker combines official, freely usable data sources – updated continuously:

This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.

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