high CVSS 7.8

CVE-2021-47311·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: net: qcom/emac: fix UAF in emac_remove adpt is netdev private data and it cannot be used after free_netdev() call. Using adpt after free_netdev() can cause UAF bug. Fix it by moving free_netdev() at the end of the function.

Severity
high
Software
Kernel
Fixed in
5.13.5
Published
2024-05-21

Affected versions

From: 5.11

Until: 5.13.5

Fixed in: 5.13.5

How to fix this CVE

Update your Linux kernel to version 5.13.5 or later to resolve a use-after-free vulnerability in the QCOM EMAC network driver that could lead to memory corruption. The fix reorders cleanup operations in the emac_remove() function to prevent accessing freed memory structures. Prioritize this update for systems running kernel versions 5.11 through 5.13.4, particularly those using Qualcomm Ethernet hardware.

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 | grep -E '^5\.(11|12|13\.[0-4])'
  2. Verify QCOM EMAC driver is loaded: lsmod | grep -i emac
  3. Search kernel logs for UAF-related crashes: dmesg | grep -i 'use.*after.*free\|UAF\|segfault' | grep -i emac
  4. Confirm kernel update: uname -r and verify version is 5.13.5 or later

FAQ

What is CVE-2021-47311?

This vulnerability is a use-after-free (UAF) bug in the QCOM EMAC Ethernet driver's removal routine, where the driver attempts to access network device private data after the device structure has been freed, potentially causing kernel crashes or memory corruption.

Is CVE-2021-47311 being actively exploited?

No, this CVE is not listed on CISA's Known Exploited Vulnerabilities (KEV) catalog and no public exploits are available. However, the high CVSS score (7.8) indicates local attackers with basic system access could trigger the vulnerability.

What versions of Kernel are affected by CVE-2021-47311?

Linux kernel versions 5.11 through 5.13.4 are vulnerable. The fix was included in kernel 5.13.5 and later stable releases.

How do I check if my server is vulnerable to CVE-2021-47311?

Run: uname -r and check if output matches 5.11.* through 5.13.[0-4]; then run: lsmod | grep emac to confirm the affected driver is present.

Does Defensia detect CVE-2021-47311?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47311 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-2024-36031CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: keys: Fix overwrite of key expiration on instantiation The expiry time of a key is unconditionally overwritten during instantiation, defaulting to turn it permanent. This causes a problem for DNS resolution as the expiration set by user-space is overwritten to TIME64_MAX, disabling further DNS updates. Fix this by restoring the condition that key_set_expiry is only called when the pre-parser sets a specific expiry.
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-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-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

Track CVEs across your fleet automatically

Defensia scans your Linux servers and tells you exactly which ones are running vulnerable versions — including CVE-2021-47311. Free for 1 server.

Get started free