high CVSS 7.1

CVE-2021-47291·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: ipv6: fix another slab-out-of-bounds in fib6_nh_flush_exceptions While running the self-tests on a KASAN enabled kernel, I observed a slab-out-of-bounds splat very similar to the one reported in commit 821bbf79fe46 ("ipv6: Fix KASAN: slab-out-of-bounds Read in fib6_nh_flush_exceptions"). We additionally need to take care of fib6_metrics initialization failure when the caller provides an nh. The fix is similar, explicitly free the route instead of calling fib6_info_release on a half-initialized object.

Severity: high
Software: Kernel
Fixed in: 5.13.6
Published: 2024-05-21

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 address this memory safety issue affecting IPv6 routing. This vulnerability in the fib6_nh_flush_exceptions function can cause kernel memory corruption when handling incomplete route initialization. Apply the patch immediately to systems running kernels 5.11 through 5.13.5.

sudo dnf check-update kernel && sudo dnf update kernel

Defensia detects this vulnerability

How to check if you are affected

Check kernel version: uname -r | grep -E '^5\.(11|12|13\.[0-5])' — if output matches, system is vulnerable
Verify if IPv6 routing is enabled: cat /proc/sys/net/ipv6/conf/all/forwarding (1=enabled, affected if enabled on vulnerable kernel)
Search kernel logs for memory corruption signs: sudo dmesg | grep -i 'kasan\|slab-out-of-bounds\|use-after-free' | grep -i fib6
Confirm patch applied: uname -r | grep -E '^5\.(13\.[6-9]|1[4-9]|[2-9][0-9])' — if kernel version is 5.13.6 or higher, vulnerability is patched

FAQ

What is CVE-2021-47291?

This vulnerability is a slab-out-of-bounds memory access in the Linux kernel's IPv6 routing subsystem, specifically in the fib6_nh_flush_exceptions function. When metric initialization fails during route setup, improper cleanup can lead to kernel memory corruption and potential system crash.

Is CVE-2021-47291 being actively exploited?

No, according to CISA's Known Exploited Vulnerabilities catalog, CVE-2021-47291 is not actively exploited in the wild, and no public exploits are publicly available.

What versions of Kernel are affected by CVE-2021-47291?

Linux kernel versions 5.11.0 through 5.13.5 are vulnerable; the issue was fixed in kernel 5.13.6 and later.

How do I check if my server is vulnerable to CVE-2021-47291?

Run 'uname -r' and compare the output against the affected range 5.11-5.13.5. If your version falls within this range and IPv6 routing is enabled (check with 'cat /proc/sys/net/ipv6/conf/all/forwarding'), your system is vulnerable.

Does Defensia detect CVE-2021-47291?

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-2021-47291 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-2024-38612CVSS 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-2024-39462CVSS 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-2024-38541CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: of: module: add buffer overflow check in of_modalias() In of_modalias(), if the buffer happens to be too small even for the 1st snprintf() call, the len parameter will become negative and str parameter (if not NULL initially) will point beyond the buffer's end. Add the buffer overflow check after the 1st snprintf() call and fix such check after the strlen() call (accounting for the terminating NUL char).

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-2021-47291. Free for 1 server.

Get started free