CVE-2023-53338: linux kernel Use-After-Free — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: lwt: Fix return values of BPF xmit ops BPF encap ops can return different types of positive values, such like NET_RX_DROP, NET_XMIT_CN, NETDEV_TX_BUSY, and so on, from function skb_do_redirect and bpf_lwt_xmit_reroute. At the xmit hook, such return values would be treated implicitly as LWTUNNEL_XMIT_CONTINUE in ip(6)_finish_output2. When this happens, skbs that have been freed would continue to the neighbor subsystem, causing use-after-free bug and kernel crashes. To fix the incorrect behavior, skb_do_redirect return values can be simply discarded, the same as tc-egress behavior. On the other hand, bpf_lwt_xmit_reroute returns useful errors to local senders, e.g. PMTU information. Thus convert its return values to avoid the conflict with LWTUNNEL_XMIT_CONTINUE.

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CVSS v3.1 Score

7.8

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-416 Use After Free

Affected Products

Vendor	Product	Versions
linux	linux_kernel	4.10 — 5.4.257
linux	linux_kernel	5.5 — 5.10.195
linux	linux_kernel	5.11 — 5.15.132
linux	linux_kernel	5.16 — 6.1.53
linux	linux_kernel	6.2 — 6.4.16
linux	linux_kernel	6.5 — 6.5.3

References

Advisories & Patches

https://git.kernel.org/stable/c/065d5f17096ec9161180e2c890afdff4dc6125f2 https://git.kernel.org/stable/c/29b22badb7a84b783e3a4fffca16f7768fb31205 https://git.kernel.org/stable/c/65583f9e070db7bece20710cfa2e3daeb0b831d9 https://git.kernel.org/stable/c/67f8f2bae8e7ac72e09def2b667e44704c4d1ee1 https://git.kernel.org/stable/c/a97f221651fcdc891166e9bc270e3d9bfa5a0080 https://git.kernel.org/stable/c/d68c17402442f5f494a2c3ebde5cb82f6aa9160a https://git.kernel.org/stable/c/e3f647e4b642f9f6d32795a16f92c116c138d2af

Frequently Asked Questions

What is CVE-2023-53338? +

In the Linux kernel, the following vulnerability has been resolved: lwt: Fix return values of BPF xmit ops BPF encap ops can return different types of positive values, such like NET_RX_DROP, NET_XMIT_CN, NETDEV_TX_BUSY, and so on, from function skb_do_redirect and bpf_lwt_xmit_reroute. At the xmit hook, such return values would be treated implicitly as LWTUNNEL_XMIT_CONTINUE in ip(6)_finish_output2. When this happens, skbs that have been freed would continue to the neighbor subsystem, causing use-after-free bug and kernel crashes. To fix the incorrect behavior, skb_do_redirect return values can be simply discarded, the same as tc-egress behavior. On the other hand, bpf_lwt_xmit_reroute returns useful errors to local senders, e.g. PMTU information. Thus convert its return values to avoid the conflict with LWTUNNEL_XMIT_CONTINUE. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2023-53338? +

CVE-2023-53338 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2023-53338? +

CVE-2023-53338 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2023-53338? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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