medium CVSS 5.5 EPSS <0.1%

CVE-2021-47297·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: net: fix uninit-value in caif_seqpkt_sendmsg When nr_segs equal to zero in iovec_from_user, the object msg->msg_iter.iov is uninit stack memory in caif_seqpkt_sendmsg which is defined in ___sys_sendmsg. So we cann't just judge msg->msg_iter.iov->base directlly. We can use nr_segs to judge msg in caif_seqpkt_sendmsg whether has data buffers. ===================================================== BUG: KMSAN: uninit-value in caif_seqpkt_sendmsg+0x693/0xf60 net/caif/caif_socket.c:542 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1c9/0x220 lib/dump_stack.c:118 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118 __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215 caif_seqpkt_sendmsg+0x693/0xf60 net/caif/caif_socket.c:542 sock_sendmsg_nosec net/socket.c:652 [inline] sock_sendmsg net/socket.c:672 [inline] ____sys_sendmsg+0x12b6/0x1350 net/socket.c:2343 ___sys_sendmsg net/socket.c:2397 [inline] __sys_sendmmsg+0x808/0xc90 net/socket.c:2480 __compat_sys_sendmmsg net/compat.c:656 [inline]

Severity
medium
Software
Kernel
Fixed in
5.13.6
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 2% 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: 5.11

Until: 5.13.6

Fixed in: 5.13.6

How to fix this CVE

Update your Linux kernel to version 5.13.6 or later to resolve a memory safety issue in the CAIF socket implementation. The vulnerability allows uninitialized stack memory to be accessed when socket messages contain zero data segments, potentially causing a denial of service. Apply the kernel update through your distribution's package manager and reboot your system to activate the patched kernel.

sudo dnf update kernel kernel-devel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Check your current kernel version: uname -r (vulnerable if 5.11.x to 5.13.5)
  2. Verify CAIF networking support is enabled: grep -i caif /boot/config-$(uname -r) (look for CONFIG_CAIF=y or CONFIG_CAIF=m)
  3. Search system logs for KMSAN warnings related to caif_seqpkt_sendmsg: sudo grep -i 'caif_seqpkt_sendmsg\|KMSAN.*uninit' /var/log/kern.log /var/log/syslog 2>/dev/null
  4. Confirm patch installation: uname -r should show 5.13.6 or later version after reboot

FAQ

What is CVE-2021-47297?

CVE-2021-47297 is a memory safety vulnerability in the Linux kernel's CAIF (Common API Framework) socket implementation where uninitialized stack memory could be accessed when sendmsg() is called with zero data segments, leading to potential system crashes or information disclosure.

Is CVE-2021-47297 being actively exploited?

No, CVE-2021-47297 is not listed on the CISA Known Exploited Vulnerabilities (KEV) catalog and no public exploits are currently available, though the vulnerability poses a denial-of-service risk.

What versions of Kernel are affected by CVE-2021-47297?

Linux kernel versions 5.11 through 5.13.5 are vulnerable; version 5.13.6 and later include the fix.

How do I check if my server is vulnerable to CVE-2021-47297?

Run: uname -r | grep -E '5\.(11|12|13\.[0-5])' - if output appears, your kernel is vulnerable; also verify CAIF is enabled with: cat /boot/config-$(uname -r) | grep CONFIG_CAIF

Does Defensia detect CVE-2021-47297?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2021-47297 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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CVE-2026-52955CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: libceph: Fix potential out-of-bounds access in crush_decode() A message of type CEPH_MSG_OSD_MAP containing a crush map with at least one bucket has two fields holding the bucket algorithm. If the values in these two fields differ, an out-of-bounds access can occur. This is the case because the first algorithm field (alg) is used to allocate the correct amount of memory for a bucket of this type, while the second algorithm field inside the bucket (b->alg) is used in the subsequent processing. This patch fixes the issue by adding a check that compares alg and b->alg and aborts the processing in case they differ. Furthermore, b->alg is set to 0 in this case, because the destruction of the crush map also uses this field to determine the bucket type, which can again result in an out-of-bounds access when trying to free the memory pointed to by the fields of the bucket. To correctly free the memory allocated for the bucket in such a case, the corresponding call to kfree is moved from the algorithm-specific crush_destroy_bucket functions to the generic crush_destroy_bucket().
CVE-2026-53384CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: serial: 8250_dw: unregister 8250 port if clk_notifier_register() fails dw8250_probe() registers the 8250 port via serial8250_register_8250_port() and then, if the device has a clock, registers a clock notifier. If clk_notifier_register() fails, probe returns the error but leaves the 8250 port registered. The matching serial8250_unregister_port() lives in dw8250_remove(), which is not called when probe fails, so the port slot stays occupied until the device is rebound or the system is rebooted. The devm-allocated driver data is freed while the port still references it (via the saved private_data and serial_in/serial_out callbacks), so any access to that port slot before a rebind is a use-after-free hazard. Unregister the port on the clk_notifier_register() error path.
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References

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