high CVSS 7.8

CVE-2021-46998·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: ethernet:enic: Fix a use after free bug in enic_hard_start_xmit In enic_hard_start_xmit, it calls enic_queue_wq_skb(). Inside enic_queue_wq_skb, if some error happens, the skb will be freed by dev_kfree_skb(skb). But the freed skb is still used in skb_tx_timestamp(skb). My patch makes enic_queue_wq_skb() return error and goto spin_unlock() incase of error. The solution is provided by Govind. See https://lkml.org/lkml/2021/4/30/961.

Severity
high
Software
Kernel
Fixed in
5.12.5
Published
2024-02-28

Affected versions

From: 5.12

Until: 5.12.5

Fixed in: 5.12.5

How to fix this CVE

Update your Linux kernel to version 5.12.5 or later to patch the use-after-free vulnerability in the enic Ethernet driver's packet transmission function. This vulnerability allows a freed memory region to be accessed after deallocation, potentially leading to kernel crashes or privilege escalation on systems using Cisco UCS virtual network adapters. Apply the kernel update as soon as possible, especially on production systems running affected versions.

sudo dnf update kernel

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed kernel version: uname -r (vulnerable if output shows 5.12.0 through 5.12.4)
  2. Verify if enic driver is loaded: lsmod | grep enic (if present, system may use affected driver)
  3. Review kernel ring buffer for memory errors: dmesg | grep -i 'use-after-free\|use after free\|uaf'
  4. Confirm fix by upgrading and checking: uname -r should show 5.12.5 or higher; verify with dmesg | tail -20 for 'enic' driver messages without errors

FAQ

What is CVE-2021-46998?

This vulnerability is a use-after-free flaw in the Linux kernel's enic Ethernet driver where freed memory is incorrectly accessed during packet transmission, potentially causing kernel instability or privilege escalation on systems with Cisco UCS virtual network adapters.

Is CVE-2021-46998 being actively exploited?

No, according to CISA's Known Exploited Vulnerabilities list, CVE-2021-46998 is not currently being actively exploited. No public exploit has been released for this vulnerability.

What versions of Kernel are affected by CVE-2021-46998?

Linux kernel versions 5.12.0 through 5.12.4 are vulnerable; the fix is included in kernel version 5.12.5 and later.

How do I check if my server is vulnerable to CVE-2021-46998?

Run 'uname -r' and check if the output falls within 5.12.0-5.12.4 range, then verify enic driver presence with 'lsmod | grep enic'. If both conditions are met, your system is vulnerable.

Does Defensia detect CVE-2021-46998?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Linux kernel is installed on a monitored server, CVE-2021-46998 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-2024-38623CVSS 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-2024-36031CVSS 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-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.
CVE-2022-48716CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ASoC: codecs: wcd938x: fix incorrect used of portid Mixer controls have the channel id in mixer->reg, which is not same as port id. port id should be derived from chan_info array. So fix this. Without this, its possible that we could corrupt struct wcd938x_sdw_priv by accessing port_map array out of range with channel id instead of port id.

References

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