high CVSS 7.8

CVE-2021-47521·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: can: sja1000: fix use after free in ems_pcmcia_add_card() If the last channel is not available then "dev" is freed. Fortunately, we can just use "pdev->irq" instead. Also we should check if at least one channel was set up.

Severity
high
Software
Kernel
Fixed in
5.15.8
Published
2024-05-24

Affected versions

From: 5.11

Until: 5.15.8

Fixed in: 5.15.8

How to fix this CVE

Update your Linux kernel to version 5.15.8 or later to resolve a use-after-free vulnerability in the EMS PCMCIA CAN driver initialization. This flaw could allow local attackers with low privileges to trigger memory corruption by exploiting improper device cleanup during multi-channel setup failure. Prioritize this patch if your system uses EMS PCMCIA CAN interfaces.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Run `uname -r` to check your current kernel version. Versions 5.11 through 5.15.7 are vulnerable.
  2. Verify if EMS PCMCIA CAN driver is loaded: `lsmod | grep sja1000` or `grep -i 'ems\|sja1000' /proc/modules`
  3. Check kernel logs for CAN device initialization errors: `dmesg | grep -i 'ems\|can.*error\|sja1000'`
  4. Confirm patch application by checking if kernel version is 5.15.8 or higher: `uname -r | grep -E '^5\.(1[5-9]|[2-9][0-9]|15\.[8-9]|15\.[1-9][0-9])'

FAQ

What is CVE-2021-47521?

This vulnerability is a use-after-free condition in the EMS PCMCIA CAN driver that occurs when multi-channel device initialization fails, allowing local attackers to cause memory corruption and potentially execute arbitrary code.

Is CVE-2021-47521 being actively exploited?

No, CVE-2021-47521 is not listed in the CISA Known Exploited Vulnerabilities catalog, and no public exploits are currently available.

What versions of Kernel are affected by CVE-2021-47521?

Kernel versions 5.11 through 5.15.7 are affected. Version 5.15.8 and later include the fix.

How do I check if my server is vulnerable to CVE-2021-47521?

Run `uname -r` to get your kernel version. If the output shows a version between 5.11 and 5.15.7, your system is vulnerable. Additionally, check if the EMS PCMCIA driver is in use with `lsmod | grep sja1000`.

Does Defensia detect CVE-2021-47521?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47521 will appear in your dashboard with remediation steps.

Related Kernel CVEs

CVE-2024-42256CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: cifs: Fix server re-repick on subrequest retry When a subrequest is marked for needing retry, netfs will call cifs_prepare_write() which will make cifs repick the server for the op before renegotiating credits; it then calls cifs_issue_write() which invokes smb2_async_writev() - which re-repicks the server. If a different server is then selected, this causes the increment of server->in_flight to happen against one record and the decrement to happen against another, leading to misaccounting. Fix this by just removing the repick code in smb2_async_writev(). As this is only called from netfslib-driven code, cifs_prepare_write() should always have been called first, and so server should never be NULL and the preparatory step is repeated in the event that we do a retry. The problem manifests as a warning looking something like: WARNING: CPU: 4 PID: 72896 at fs/smb/client/smb2ops.c:97 smb2_add_credits+0x3f0/0x9e0 [cifs] ... RIP: 0010:smb2_add_credits+0x3f0/0x9e0 [cifs] ... smb2_writev_callback+0x334/0x560 [cifs] cifs_demultiplex_thread+0x77a/0x11b0 [cifs] kthread+0x187/0x1d0 ret_from_fork+0x34/0x60 ret_from_fork_asm+0x1a/0x30 Which may be triggered by a number of different xfstests running against an Azure server in multichannel mode. generic/249 seems the most repeatable, but generic/215, generic/249 and generic/308 may also show it.
CVE-2024-39462CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: clk: bcm: dvp: Assign ->num before accessing ->hws Commit f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with __counted_by") annotated the hws member of 'struct clk_hw_onecell_data' with __counted_by, which informs the bounds sanitizer about the number of elements in hws, so that it can warn when hws is accessed out of bounds. As noted in that change, the __counted_by member must be initialized with the number of elements before the first array access happens, otherwise there will be a warning from each access prior to the initialization because the number of elements is zero. This occurs in clk_dvp_probe() due to ->num being assigned after ->hws has been accessed: UBSAN: array-index-out-of-bounds in drivers/clk/bcm/clk-bcm2711-dvp.c:59:2 index 0 is out of range for type 'struct clk_hw *[] __counted_by(num)' (aka 'struct clk_hw *[]') Move the ->num initialization to before the first access of ->hws, which clears up the warning.
CVE-2024-38623CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: Use variable length array instead of fixed size Should fix smatch warning: ntfs_set_label() error: __builtin_memcpy() 'uni->name' too small (20 vs 256)
CVE-2024-38612CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ipv6: sr: fix invalid unregister error path The error path of seg6_init() is wrong in case CONFIG_IPV6_SEG6_LWTUNNEL is not defined. In that case if seg6_hmac_init() fails, the genl_unregister_family() isn't called. This issue exist since commit 46738b1317e1 ("ipv6: sr: add option to control lwtunnel support"), and commit 5559cea2d5aa ("ipv6: sr: fix possible use-after-free and null-ptr-deref") replaced unregister_pernet_subsys() with genl_unregister_family() in this error path.
CVE-2021-47548CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ethernet: hisilicon: hns: hns_dsaf_misc: fix a possible array overflow in hns_dsaf_ge_srst_by_port() The if statement: if (port >= DSAF_GE_NUM) return; limits the value of port less than DSAF_GE_NUM (i.e., 8). However, if the value of port is 6 or 7, an array overflow could occur: port_rst_off = dsaf_dev->mac_cb[port]->port_rst_off; because the length of dsaf_dev->mac_cb is DSAF_MAX_PORT_NUM (i.e., 6). To fix this possible array overflow, we first check port and if it is greater than or equal to DSAF_MAX_PORT_NUM, the function returns.

References

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