high CVSS 7.8

CVE-2023-52906·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_mpls: Fix warning during failed attribute validation The 'TCA_MPLS_LABEL' attribute is of 'NLA_U32' type, but has a validation type of 'NLA_VALIDATE_FUNCTION'. This is an invalid combination according to the comment above 'struct nla_policy': " Meaning of `validate' field, use via NLA_POLICY_VALIDATE_FN: NLA_BINARY Validation function called for the attribute. All other Unused - but note that it's a union " This can trigger the warning [1] in nla_get_range_unsigned() when validation of the attribute fails. Despite being of 'NLA_U32' type, the associated 'min'/'max' fields in the policy are negative as they are aliased by the 'validate' field. Fix by changing the attribute type to 'NLA_BINARY' which is consistent with the above comment and all other users of NLA_POLICY_VALIDATE_FN(). As a result, move the length validation to the validation function. No regressions in MPLS tests: # ./tdc.py -f tc-tests/actions/mpls.json [...] # echo $? 0 [1] WARNING: CPU: 0 PID: 17743 at lib/nlattr.c:118 nla_get_range_unsigned+0x1d8/0x1e0 lib/nlattr.c:117 Modules linked in: CPU: 0 PID: 17743 Comm: syz-executor.0 Not tainted 6.1.0-rc8 #3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-48-gd9c812dda519-prebuilt.qemu.org 04/01/2014 RIP: 0010:nla_get_range_unsigned+0x1d8/0x1e0 lib/nlattr.c:117 [...] Call Trace: <TASK> __netlink_policy_dump_write_attr+0x23d/0x990 net/netlink/policy.c:310 netlink_policy_dump_write_attr+0x22/0x30 net/netlink/policy.c:411 netlink_ack_tlv_fill net/netlink/af_netlink.c:2454 [inline] netlink_ack+0x546/0x760 net/netlink/af_netlink.c:2506 netlink_rcv_skb+0x1b7/0x240 net/netlink/af_netlink.c:2546 rtnetlink_rcv+0x18/0x20 net/core/rtnetlink.c:6109 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x5e9/0x6b0 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x739/0x860 net/netlink/af_netlink.c:1921 sock_sendmsg_nosec net/socket.c:714 [inline] sock_sendmsg net/socket.c:734 [inline] ____sys_sendmsg+0x38f/0x500 net/socket.c:2482 ___sys_sendmsg net/socket.c:2536 [inline] __sys_sendmsg+0x197/0x230 net/socket.c:2565 __do_sys_sendmsg net/socket.c:2574 [inline] __se_sys_sendmsg net/socket.c:2572 [inline] __x64_sys_sendmsg+0x42/0x50 net/socket.c:2572 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Severity
high
Software
Kernel
Fixed in
6.1.7
Published
2024-08-21

Affected versions

From: 5.16

Until: 6.1.7

Fixed in: 6.1.7

How to fix this CVE

Update your Linux kernel to version 6.1.7 or later to resolve this netlink attribute validation flaw in the MPLS traffic control module. The vulnerability stems from a mismatch between attribute type declaration and validation function usage, which can trigger kernel warnings during failed policy validation. Apply the update through your distribution's package manager to ensure the kernel patch is installed and active after reboot.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Check kernel version: uname -r — verify it is 6.1.7 or later; versions 5.16 through 6.1.6 are vulnerable
  2. Verify MPLS traffic control module presence: lsmod | grep mpls — check if act_mpls is loaded
  3. Review kernel logs for validation warnings: dmesg | grep -i 'nla_get_range_unsigned' — look for netlink attribute range validation warnings
  4. Confirm patch applied: grep -i 'TCA_MPLS_LABEL' /boot/config-$(uname -r) — ensure kernel configuration includes MPLS support; reboot after kernel update and re-run uname -r to confirm fixed version is running

FAQ

What is CVE-2023-52906?

A Linux kernel vulnerability in the MPLS traffic control module where the TCA_MPLS_LABEL attribute was incorrectly configured with a validation function mismatch, causing kernel warnings and potential system instability during netlink policy validation.

Is CVE-2023-52906 being actively exploited?

No, CVE-2023-52906 is not listed on the CISA Known Exploited Vulnerabilities catalog and no public exploits are available. However, it should still be patched to prevent kernel warnings and maintain system reliability.

What versions of Kernel are affected by CVE-2023-52906?

Linux kernel versions 5.16 through 6.1.6 are vulnerable. The fix is included in kernel 6.1.7 and later.

How do I check if my server is vulnerable to CVE-2023-52906?

Run 'uname -r' and compare your kernel version against 6.1.7; if your version is between 5.16 and 6.1.6, you are vulnerable and should update immediately.

Does Defensia detect CVE-2023-52906?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2023-52906 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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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.
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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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