ipv6: rpl: reserve mac_len headroom when recompressed SRH grows
Summary
| CVE | CVE-2026-43501 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-21 13:16:19 UTC |
| Updated | 2026-07-02 12:17:19 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 7.5 HIGH from ADP
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS: 0.000700000 probability, percentile 0.215780000 (date 2026-06-04)
Problem Types: CWE-787 | CWE-131 | CWE-131 Incorrect Calculation of Buffer Size
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | ADP | CVSS | 7.5 | HIGH | CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
| 3.1 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | Secondary | 9.8 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| 3.1 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | Secondary | 7.5 | HIGH | CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
| 3.1 | CNA | DECLARED | 9.8 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
CVSS v3.1 Breakdown
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Operating System | Linux | Linux Kernel | All | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 bde199c72d319a4e207f88daabc888317504e2fb git | Not specified |
| CNA | Linux | Linux | affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 be1fa0aa9b4fdd5a8b7a61ba520a690a68391e6e git | Not specified |
| CNA | Linux | Linux | affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 0a9e8053f1f8a8e1bfc1dd61ffe67be6c1180402 git | Not specified |
| CNA | Linux | Linux | affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 8e8be63465a5e80394c70324603dfea1bfdad48f git | Not specified |
| CNA | Linux | Linux | affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 4babc2d9fda2df43823b85d08a0180b68f1b0854 git | Not specified |
| CNA | Linux | Linux | affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 c261d07a80576dc8ccf394ef8f074f8c67a06b37 git | Not specified |
| CNA | Linux | Linux | affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 7398ebefbfd4f8a31d4f665a4213302fa995494b git | Not specified |
| CNA | Linux | Linux | affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 9e6bf146b55999a095bb14f73a843942456d1adc git | Not specified |
| CNA | Linux | Linux | affected 5.7 | Not specified |
| CNA | Linux | Linux | unaffected 5.7 semver | Not specified |
| CNA | Linux | Linux | unaffected 5.10.258 5.10.* semver | Not specified |
| CNA | Linux | Linux | unaffected 5.15.209 5.15.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.1.175 6.1.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.6.140 6.6.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.12.86 6.12.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.27 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.0.4 7.0.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.1 * original_commit_for_fix | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux AppStream EUS V. 10.0 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux AppStream V. 10 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux AppStream E4S V.9.2 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux AppStream E4S V.9.4 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux AppStream EUS V.9.6 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux AppStream V. 9 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux BaseOS EUS V. 10.0 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux BaseOS V. 10 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux BaseOS E4S V.9.2 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux BaseOS E4S V.9.4 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux BaseOS EUS V.9.6 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux BaseOS V. 9 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux CodeReady Linux Builder EUS V. 10.0 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux CodeReady Linux Builder V. 10 | Not specified | Not specified |
| ADP | Red Hat | Red Hat CodeReady Linux Builder EUS V.9.6 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux CodeReady Linux Builder V. 9 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux Real Time For NFV EUS V. 10.0 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux Real Time For NFV V. 10 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux Real Time For NFV E4S V.9.2 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux Real Time For NFV E4S V.9.4 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux Real Time For NFV EUS V.9.6 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux Real Time For NFV V. 9 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux Real Time EUS V. 10.0 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux Real Time V. 10 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux Real Time E4S V.9.2 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux Real Time E4S V.9.4 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux Real Time EUS V.9.6 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux Real Time V. 9 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 9 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 6 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 7 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8 | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/8e8be63465a5e80394c70324603dfea1bfdad48f | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | Patch |
| git.kernel.org/stable/c/c261d07a80576dc8ccf394ef8f074f8c67a06b37 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | Patch |
| access.redhat.com/errata/RHSA-2026:25217 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:25191 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:34095 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| git.kernel.org/stable/c/0a9e8053f1f8a8e1bfc1dd61ffe67be6c1180402 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | Patch |
| git.kernel.org/stable/c/bde199c72d319a4e207f88daabc888317504e2fb | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | Patch |
| access.redhat.com/errata/RHSA-2026:27713 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:27731 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| git.kernel.org/stable/c/7398ebefbfd4f8a31d4f665a4213302fa995494b | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | Patch |
| bugzilla.redhat.com/show_bug.cgi | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | bugzilla.redhat.com | |
| git.kernel.org/stable/c/4babc2d9fda2df43823b85d08a0180b68f1b0854 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | Patch |
| access.redhat.com/errata/RHSA-2026:33900 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/security/cve/CVE-2026-43501 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43501.json | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | security.access.redhat.com | |
| git.kernel.org/stable/c/9e6bf146b55999a095bb14f73a843942456d1adc | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | Patch |
| access.redhat.com/errata/RHSA-2026:34094 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| git.kernel.org/stable/c/be1fa0aa9b4fdd5a8b7a61ba520a690a68391e6e | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | Patch |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| ADP | 2026-05-21T00:00:00.000Z | Reported to Red Hat. |
| ADP | 2026-05-21T00:00:00.000Z | Made public. |
Solutions
ADP: RHSA-2026:27731: Red Hat Enterprise Linux AppStream EUS (v. 10.0), Red Hat Enterprise Linux BaseOS EUS (v. 10.0), Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0), Red Hat Enterprise Linux Real Time EUS (v. 10.0), Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0)
ADP: RHSA-2026:25191: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10), Red Hat Enterprise Linux Real Time (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10)
ADP: RHSA-2026:34095: Red Hat Enterprise Linux AppStream E4S (v.9.2), Red Hat Enterprise Linux BaseOS E4S (v.9.2)
ADP: RHSA-2026:27713: Red Hat Enterprise Linux AppStream E4S (v.9.4), Red Hat Enterprise Linux BaseOS E4S (v.9.4), Red Hat Enterprise Linux Real Time E4S (v.9.4), Red Hat Enterprise Linux Real Time for NFV E4S (v.9.4)
ADP: RHSA-2026:34094: Red Hat CodeReady Linux Builder EUS (v.9.6), Red Hat Enterprise Linux AppStream EUS (v.9.6), Red Hat Enterprise Linux BaseOS EUS (v.9.6), Red Hat Enterprise Linux Real Time EUS (v.9.6), Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6)
ADP: RHSA-2026:25217: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9)
ADP: RHSA-2026:33900: Red Hat Enterprise Linux Real Time E4S (v.9.2), Red Hat Enterprise Linux Real Time for NFV E4S (v.9.2)
Workarounds
ADP: To mitigate this issue, disable IPv6 Source Routing by setting the `accept_source_route` sysctl parameter to 0 for all IPv6 interfaces. This can prevent the kernel from processing IPv6 Source Routing Headers, thereby avoiding the vulnerable code path. To disable IPv6 Source Routing: `sysctl -w net.ipv6.conf.all.accept_source_route=0` `sysctl -w net.ipv6.conf.default.accept_source_route=0` To make this change persistent across reboots, add the following lines to `/etc/sysctl.d/99-disable-ipv6-srh.conf`: `net.ipv6.conf.all.accept_source_route = 0` `net.ipv6.conf.default.accept_source_route = 0` Then, apply the changes with: `sysctl --system` Disabling IPv6 Source Routing may impact network configurations that rely on this feature.