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CVE-2026-43038— ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ip6_err_gen_icmpv6_unreach函数未清除skb2的cb数组，导致IPv4 cb结构被错误解释为IPv6 cb结构，可能引发越界扫描。

CVSS 9.8 · Critical EPSS 0.26% · P16

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux ca15a078bd907df5fc1c009477869c5cbde3b753< c438ba010171b70bad22fc18b1d5bdc3627476e8 affected
ca15a078bd907df5fc1c009477869c5cbde3b753< 0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7 affected
ca15a078bd907df5fc1c009477869c5cbde3b753< a4437faf135da293d16fcc4cc607316742bd0ebb affected
ca15a078bd907df5fc1c009477869c5cbde3b753< 3d5127d998de617b130aae96b138dba22ac6a8a7 affected
ca15a078bd907df5fc1c009477869c5cbde3b753< e41953e7d118e2702bcb217879c173d9d1d3cd4e affected
ca15a078bd907df5fc1c009477869c5cbde3b753< a2edbb6393972a02114b6003953a5cef3104fada affected
ca15a078bd907df5fc1c009477869c5cbde3b753< 1ceeebd5bd6d855b17a5df625109bfe29129d7cf affected
ca15a078bd907df5fc1c009477869c5cbde3b753< 86ab3e55673a7a49a841838776f1ab18d23a67b5 affected
… +10 more rows
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I. Basic Information for CVE-2026-43038

Vulnerability Information
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Vulnerability Title
ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach() Sashiko AI-review observed: In ip6_err_gen_icmpv6_unreach(), the skb is an outer IPv4 ICMP error packet where its cb contains an IPv4 inet_skb_parm. When skb is cloned into skb2 and passed to icmp6_send(), it uses IP6CB(skb2). IP6CB interprets the IPv4 inet_skb_parm as an inet6_skb_parm. The cipso offset in inet_skb_parm.opt directly overlaps with dsthao in inet6_skb_parm at offset 18. If an attacker sends a forged ICMPv4 error with a CIPSO IP option, dsthao would be a non-zero offset. Inside icmp6_send(), mip6_addr_swap() is called and uses ipv6_find_tlv(skb, opt->dsthao, IPV6_TLV_HAO). This would scan the inner, attacker-controlled IPv6 packet starting at that offset, potentially returning a fake TLV without checking if the remaining packet length can hold the full 18-byte struct ipv6_destopt_hao. Could mip6_addr_swap() then perform a 16-byte swap that extends past the end of the packet data into skb_shared_info? Should the cb array also be cleared in ip6_err_gen_icmpv6_unreach() and ip6ip6_err() to prevent this? This patch implements the first suggestion. I am not sure if ip6ip6_err() needs to be changed. A separate patch would be better anyway.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ip6_err_gen_icmpv6_unreach函数未清除skb2的cb数组，导致IPv4 cb结构被错误解释为IPv6 cb结构，可能引发越界扫描。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

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Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux ca15a078bd907df5fc1c009477869c5cbde3b753 ~ c438ba010171b70bad22fc18b1d5bdc3627476e8 -
Linux Linux 3.13 -

II. Public POCs for CVE-2026-43038

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III. Intelligence Information for CVE-2026-43038

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Patches & Fixes for CVE-2026-43038 (8)

Same Patch Batch · Linux · 2026-05-01 · 146 CVEs total

CVE-2026-43011 9.8 CRITICAL net/x25: Fix potential double free of skb
CVE-2026-43037 9.8 CRITICAL ip6_tunnel: clear skb2->cb[] in ip4ip6_err()
CVE-2026-31705 9.8 CRITICAL ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment
CVE-2026-43039 9.8 CRITICAL net: ti: icssg-prueth: fix missing data copy and wrong recycle in ZC RX dispatch
CVE-2026-31718 9.8 CRITICAL ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger
CVE-2026-43018 8.8 HIGH Bluetooth: hci_event: fix potential UAF in hci_le_remote_conn_param_req_evt
CVE-2026-31773 8.8 HIGH Bluetooth: SMP: derive legacy responder STK authentication from MITM state
CVE-2026-31739 8.8 HIGH crypto: tegra - Add missing CRYPTO_ALG_ASYNC
CVE-2026-31735 8.8 HIGH iommupt: Fix short gather if the unmap goes into a large mapping
CVE-2026-31717 8.8 HIGH ksmbd: validate owner of durable handle on reconnect
CVE-2026-31706 8.8 HIGH ksmbd: validate num_aces and harden ACE walk in smb_inherit_dacl()
CVE-2026-43048 8.8 HIGH HID: core: Mitigate potential OOB by removing bogus memset()
CVE-2026-31709 8.8 HIGH smb: client: validate the whole DACL before rewriting it in cifsacl
CVE-2026-31712 8.3 HIGH ksmbd: require minimum ACE size in smb_check_perm_dacl()
CVE-2026-31771 8.1 HIGH Bluetooth: hci_event: move wake reason storage into validated event handlers
CVE-2026-31779 8.1 HIGH wifi: iwlwifi: mvm: fix potential out-of-bounds read in iwl_mvm_nd_match_info_handler()
CVE-2026-31708 8.1 HIGH smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path
CVE-2026-43051 8.1 HIGH HID: wacom: fix out-of-bounds read in wacom_intuos_bt_irq
CVE-2026-31780 7.8 HIGH wifi: wilc1000: fix u8 overflow in SSID scan buffer size calculation
CVE-2026-31782 7.8 HIGH perf/x86: Fix potential bad container_of in intel_pmu_hw_config

Showing top 20 of 146 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-43038

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