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CVE-2026-43501— ipv6: rpl: reserve mac_len headroom when recompressed SRH grows

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ipv6: rpl中重压缩SRH增长时未预留mac_len头部空间，可能导致内存越界写入。

CVSS 9.8 · Critical EPSS 0.63% · P47

Possible ATT&CK Techniques 1 AI

T1498 · Network Denial of Service

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3< bde199c72d319a4e207f88daabc888317504e2fb affected
8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3< be1fa0aa9b4fdd5a8b7a61ba520a690a68391e6e affected
8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3< 0a9e8053f1f8a8e1bfc1dd61ffe67be6c1180402 affected
8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3< 8e8be63465a5e80394c70324603dfea1bfdad48f affected
8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3< 4babc2d9fda2df43823b85d08a0180b68f1b0854 affected
8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3< c261d07a80576dc8ccf394ef8f074f8c67a06b37 affected
8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3< 7398ebefbfd4f8a31d4f665a4213302fa995494b affected
8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3< 9e6bf146b55999a095bb14f73a843942456d1adc affected
… +10 more rows
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I. Basic Information for CVE-2026-43501

Vulnerability Information
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Vulnerability Title
ipv6: rpl: reserve mac_len headroom when recompressed SRH grows
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ipv6: rpl: reserve mac_len headroom when recompressed SRH grows ipv6_rpl_srh_rcv() decompresses an RFC 6554 Source Routing Header, swaps the next segment into ipv6_hdr->daddr, recompresses, then pulls the old header and pushes the new one plus the IPv6 header back. The recompressed header can be larger than the received one when the swap reduces the common-prefix length the segments share with daddr (CmprI=0, CmprE>0, seg[0][0] != daddr[0] gives the maximum +8 bytes). pskb_expand_head() was gated on segments_left == 0, so on earlier segments the push consumed unchecked headroom. Once skb_push() leaves fewer than skb->mac_len bytes in front of data, skb_mac_header_rebuild()'s call to: skb_set_mac_header(skb, -skb->mac_len); will store (data - head) - mac_len into the u16 mac_header field, which wraps to ~65530, and the following memmove() writes mac_len bytes ~64KiB past skb->head. A single AF_INET6/SOCK_RAW/IPV6_HDRINCL packet over lo with a two segment type-3 SRH (CmprI=0, CmprE=15) reaches headroom 8 after one pass; KASAN reports a 14-byte OOB write in ipv6_rthdr_rcv. Fix this by expanding the head whenever the remaining room is less than the push size plus mac_len, and request that much extra so the rebuilt MAC header fits afterwards.
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ipv6: rpl中重压缩SRH增长时未预留mac_len头部空间，可能导致内存越界写入。
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)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 ~ bde199c72d319a4e207f88daabc888317504e2fb -
Linux Linux 5.7 -

II. Public POCs for CVE-2026-43501

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III. Intelligence Information for CVE-2026-43501

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Patches & Fixes for CVE-2026-43501 (8)

Same Patch Batch · Linux · 2026-05-21 · 8 CVEs total

CVE-2026-43495 8.8 HIGH net: wwan: t7xx: validate port_count against message length in t7xx_port_enum_msg_handler
CVE-2026-43502 7.8 HIGH net/rds: handle zerocopy send cleanup before the message is queued
CVE-2026-43498 7.8 HIGH accel/ivpu: Disallow re-exporting imported GEM objects
CVE-2026-43499 7.8 HIGH rtmutex: Use waiter::task instead of current in remove_waiter()
CVE-2026-43494 7.8 HIGH net/rds: reset op_nents when zerocopy page pin fails
CVE-2026-43497 7.3 HIGH fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free
CVE-2026-43496 net/sched: sch_red: Replace direct dequeue call with peek and qdisc_dequeue_peeked

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-43501

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