CVE-2026-52939

Linux kernel: null pointer dereference

Risk score: 48/100
CVSS: 5.5 v3.1
Exploit chance (30 days): 0.1%
Published: 24 Jun 2026

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What to know

What it is: In the Linux kernel, the following vulnerability has been resolved: net/rds: fix NULL deref in rds_ib_send_cqe_handler() on masked atomic completion rds_ib_xmit_atomic() always programs a masked atomic opcode (IB_WR_MASKED_ATOMIC_CMP_AND_SWP or IB_WR_MASKED_ATOMIC_FETCH_AND_ADD) for every RDS atomic cmsg. But the comp…
Affected: Linux kernel
Fix: Apply the vendor's security update; see the linked advisory.
Exploitation: No known exploitation

Story map

Story map: the flaws, the fix, how it unfolded and what it connects to. Boxes link to the record or article.

At a glance

Linux kernel: Amber, patch this week. In the Linux kernel, the following vulnerability has been resolved: ipv6: sr: restore network header before routing and forwarding ipv6_srh_rcv() runs with skb->data at the Segment Routing Header (SRH) while skb_network_header() points at the IPv6 header. When segments_left > 0, ipv6_srh_rcv() previously restored the …

The flaws

CVE-2026-52939: Null pointer dereference (CVSS 5.5 · EPSS 0%)
CVE-2026-98096: Out-of-bounds write (CVSS 7.4 · EPSS 1%)
CVE-2026-98115: Race condition (CVSS 8.8 · EPSS 0%)
CVE-2026-98117: Use-after-free (CVSS 7.8 · EPSS 0%)

The fix

Fix: Apply the vendor's security update; see the linked advisory.

Who is exposed: Linux kernel

Where it stands

No known exploitation

How it unfolded

6 Nov, Ubuntu security notices (official): USN-9002-1: Linux kernel (NVIDIA Tegra) vulnerabilities

Connects to

Same weakness: Null pointer dereference (CWE-476). 144 other warnings in 30 days
Same product: Earlier Linux kernel warnings. 156 in the last 90 days

Why it is Yellow

CVSS 5.5 medium
On your watchlist: linux kernel
Named in a government or vendor bulletin

Government and vendor bulletins

USN-9002-1: Linux kernel (NVIDIA Tegra) vulnerabilities

References

Original description

In the Linux kernel, the following vulnerability has been resolved: net/rds: fix NULL deref in rds_ib_send_cqe_handler() on masked atomic completion rds_ib_xmit_atomic() always programs a masked atomic opcode (IB_WR_MASKED_ATOMIC_CMP_AND_SWP or IB_WR_MASKED_ATOMIC_FETCH_AND_ADD) for every RDS atomic cmsg. But the completion-side switch in rds_ib_send_unmap_op() only handles the non-masked opcodes, so a masked atomic completion falls through to default and returns rm == NULL while send->s_op is left set. rds_ib_send_cqe_handler() then dereferences the NULL rm via rm->m_final_op, oopsing in softirq context. An unprivileged AF_RDS sendmsg() of an atomic cmsg over an active RDS/IB connection triggers it; on hardware that natively accepts masked atomics (mlx4, mlx5) no extra setup is needed. RDS/IB: rds_ib_send_unmap_op: unexpected opcode 0xd in WR! Oops: general protection fault [#1] SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000190-0x0000000000000197] RIP: rds_ib_send_cqe_handler+0x25c/0xb10 (net/rds/ib_send.c:282) Call Trace: <IRQ> rds_ib_send_cqe_handler (net/rds/ib_send.c:282) poll_scq (net/rds/ib_cm.c:274) rds_ib_tasklet_fn_send (net/rds/ib_cm.c:294) tasklet_action_common (kernel/softirq.c:943) handle_softirqs (kernel/softirq.c:573) run_ksoftirqd (kernel/softirq.c:479) </IRQ> Kernel panic - not syncing: Fatal exception in interrupt Handle the masked atomic opcodes in the same case as the non-masked ones: they map to the same struct rds_message.atomic union member, so the existing container_of()/rds_ib_send_unmap_atomic() body is correct for them.

Last activity 6 Nov 2026. Patch Forecast updates every hour.