medium CVSS 5.5 EPSS <0.1%

CVE-2021-47265·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: RDMA: Verify port when creating flow rule Validate port value provided by the user and with that remove no longer needed validation by the driver. The missing check in the mlx5_ib driver could cause to the below oops. Call trace: _create_flow_rule+0x2d4/0xf28 [mlx5_ib] mlx5_ib_create_flow+0x2d0/0x5b0 [mlx5_ib] ib_uverbs_ex_create_flow+0x4cc/0x624 [ib_uverbs] ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0xd4/0x150 [ib_uverbs] ib_uverbs_cmd_verbs.isra.7+0xb28/0xc50 [ib_uverbs] ib_uverbs_ioctl+0x158/0x1d0 [ib_uverbs] do_vfs_ioctl+0xd0/0xaf0 ksys_ioctl+0x84/0xb4 __arm64_sys_ioctl+0x28/0xc4 el0_svc_common.constprop.3+0xa4/0x254 el0_svc_handler+0x84/0xa0 el0_svc+0x10/0x26c Code: b9401260 f9615681 51000400 8b001c20 (f9403c1a)

Severity
medium
Software
Kernel
Fixed in
5.12.11
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at <0.1% — higher than 1% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Affected versions

From: 3.12

Until: 5.12.11

Fixed in: 5.12.11

How to fix this CVE

Update your Linux kernel to version 5.12.11 or later to fix a port validation flaw in RDMA flow rule creation that could cause kernel crashes. This vulnerability affects the mlx5_ib driver and related RDMA subsystems when unprivileged users supply invalid port parameters. Apply the kernel update through your distribution's package manager and reboot the system to complete remediation.

sudo dnf update kernel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed kernel version: uname -r (ensure version is 5.12.11 or later)
  2. Verify RDMA subsystem is loaded: lsmod | grep rdma (confirms if RDMA modules are active)
  3. Search kernel logs for crash signatures: sudo dmesg | grep -i 'oops\|segfault\|kernel panic' (look for _create_flow_rule or mlx5_ib references)
  4. Confirm patch applied: grep -i 'RDMA.*port.*validation' /var/log/apt/history.log or dnf history (verify kernel update was installed)

FAQ

What is CVE-2021-47265?

CVE-2021-47265 is a kernel vulnerability in the RDMA subsystem where missing port validation when creating flow rules allows unprivileged users to trigger kernel oops and denial of service. The mlx5_ib driver was particularly vulnerable to crashes when receiving invalid port parameters.

Is CVE-2021-47265 being actively exploited?

No, CVE-2021-47265 is not listed in the CISA Known Exploited Vulnerabilities catalog and no public exploits are available. However, it can be triggered by local unprivileged users with access to RDMA interfaces.

What versions of Kernel are affected by CVE-2021-47265?

Kernel versions 3.12 through 5.12.10 are affected. The vulnerability was fixed in kernel 5.12.11 and all subsequent stable releases.

How do I check if my server is vulnerable to CVE-2021-47265?

Run 'uname -r' to check your kernel version. If the output shows a version between 3.12 and 5.12.10, you are vulnerable. Additionally, confirm RDMA is in use with 'lsmod | grep rdma' or 'lsmod | grep mlx5'.

Does Defensia detect CVE-2021-47265?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47265 will appear in your dashboard with remediation steps.

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References

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