CVE-2026-43501ipv6: rpl: reserve mac_len headroom when recompressed SRH grows
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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.
- CVSS
- 9.8 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-131
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Modified
- Record last updated
- Oct 16, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | from 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 before bde199c72d319a4e207f88daabc888317504e2fb; from 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 before be1fa0aa9b4fdd5a8b7a61ba520a690a68391e6e; 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 builds before 0a9e8053f1f8a8e1bfc1dd61ffe67be6c1180402; 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 builds before 8e8be63465a5e80394c70324603dfea1bfdad48f; 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 builds before 4babc2d9fda2df43823b85d08a0180b68f1b0854; from 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 before c261d07a80576dc8ccf394ef8f074f8c67a06b37; 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 builds before 7398ebefbfd4f8a31d4f665a4213302fa995494b; 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 builds before 9e6bf146b55999a095bb14f73a843942456d1adc | CNA record |
Red Hat Red Hat Enterprise Linux 10 redhat:enterprise_linux | from 0:6.12.0-211.22.1.el10_2 not affected | CISA ADP |
Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support redhat:enterprise_linux_eus | from 0:6.12.0-55.82.1.el10_0 not affected | CISA ADP |
from 0:5.14.0-284.178.1.el9_2 not affected | CISA ADP | |
Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support redhat:rhel_eus | from 0:5.14.0-570.125.1.el9_6 not affected | CISA ADP |
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
linux linux_kernel linux:linux_kernel | from 5.7 before 5.10.258; from 5.11 before 5.15.209; from 5.16 before 6.1.175; from 6.2 before 6.6.140; from 6.7 before 6.12.86; from 6.13 before 6.18.27; from 6.19 before 7.0.4; 7.1 | NVD |
References
- https://git.kernel.org/stable/c/bde199c72d319a4e207f88daabc888317504e2fbpatch
- https://git.kernel.org/stable/c/be1fa0aa9b4fdd5a8b7a61ba520a690a68391e6epatch
- https://git.kernel.org/stable/c/0a9e8053f1f8a8e1bfc1dd61ffe67be6c1180402patch
- https://git.kernel.org/stable/c/8e8be63465a5e80394c70324603dfea1bfdad48fpatch
- https://git.kernel.org/stable/c/4babc2d9fda2df43823b85d08a0180b68f1b0854patch
- https://git.kernel.org/stable/c/c261d07a80576dc8ccf394ef8f074f8c67a06b37patch
- https://git.kernel.org/stable/c/7398ebefbfd4f8a31d4f665a4213302fa995494bpatch
- https://git.kernel.org/stable/c/9e6bf146b55999a095bb14f73a843942456d1adcpatch
- https://access.redhat.com/errata/RHSA-2026:25191
- https://access.redhat.com/errata/RHSA-2026:25217
- https://access.redhat.com/errata/RHSA-2026:27713
- https://access.redhat.com/errata/RHSA-2026:27731
- https://access.redhat.com/errata/RHSA-2026:33900
- https://access.redhat.com/errata/RHSA-2026:34094
- https://access.redhat.com/errata/RHSA-2026:34095
- https://access.redhat.com/security/cve/CVE-2026-43501
- https://bugzilla.redhat.com/show_bug.cgi?id=2480457
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43501.json
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.