Skip to main content
Public proof of conceptFix available

CVE-2026-43501

A public proof of concept exists; no exploitation attested.

  • Published2026-05-21
  • Fixed in7.0.4 · 6.18.27 · 6.12.86 · 6.6.140 · 6.1.175 · 5.15.209
  • WeaknessCWE-131 · CWE-787

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2026-05-2113:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 15:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-43501?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-43501?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Linux linux kernel
BranchAffectedFixed in
7.0≥ 6.19, < 7.0.47.0.4
6.x≥ 6.13, < 6.18.276.18.27
6.x≥ 6.7, < 6.12.866.12.86
6.x≥ 6.2, < 6.6.1406.6.140
6.1≥ 5.16, < 6.1.1756.1.175
5.x≥ 5.11, < 5.15.2095.15.209
5.x≥ 5.7, < 5.10.2585.10.258
7.1= 7.1no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • kernelAlmaLinux:10all versions · fixed in 6.12.0-211.22.1.el10_2and 74 other packages
  • kernelAlmaLinux:9all versions · fixed in 5.14.0-687.15.1.el9_8and 73 other packages

Vendor advisories

  • CVE-2026-43501 Red Hat Product Security1,658 products fixed · 22 known affected

    kernel: ipv6: rpl: reserve mac_len headroom when recompressed SRH grows

    kernel-rt as a component of Red Hat Enterprise Linux 9 · kernel-rt-core as a component of Red Hat Enterprise Linux 9 · kernel-rt-debug as a component of Red Hat Enterprise Linux 9 · +19 more

  • ICSA-26-295-11 CISA5 known affected

    Siemens SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP

    SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= V3.1.7 · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= V3.1.7 · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= V3.1.7 · +2 more

  • SSA-457936 Siemens ProductCERT5 known affected

    SSA-457936: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP V3.1.7

    SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= V3.1.7 · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= V3.1.7 · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= V3.1.7 · +2 more

  • SSA-019113 Siemens ProductCERT5 known affected

    SSA-019113: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP V3.1.6

    SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= V3.1.6 · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= V3.1.6 · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= V3.1.6 · +2 more

  • RHSA-2026:34094 Red Hat Product Security305 products fixed

    Red Hat Security Advisory: kernel security, bug fix, and enhancement update

  • RHSA-2026:34095 Red Hat Product Security167 products fixed

    Red Hat Security Advisory: kernel security, bug fix, and enhancement update

5 more advisories

Full record on NVD

Fix

  1. Update Linux linux kernel to 7.0.4 · 6.18.27 · 6.12.86 · 6.6.140 · 6.1.175 · 5.15.209 · 5.10.258
  2. Vendor fix Red Hat Product Security RHSA-2026:34094 · 305 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 The system must be rebooted for this update to take effect.
  3. Workaround from the vendor Red Hat Product Security RHSA-2026:34094 · 305 productsTo 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…
  4. Mitigation from the vendor CISA ICSA-26-295-11 · 5 productsLimit access to the interactive shell of the additional GNU/Linux subssytem to trusted personnel only.
  5. Mitigation from the vendor CISA ICSA-26-295-11 · 5 productsOnly build and run applications from trusted sources.
  6. Mitigation from the vendor Siemens ProductCERT SSA-457936 · 5 productsLimit access to the interactive shell of the additional GNU/Linux subssytem to trusted personnel only.
  7. Mitigation from the vendor Siemens ProductCERT SSA-457936 · 5 productsOnly build and run applications from trusted sources.

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
2 repositories, unverifiedngtuonghung/CVE-2026-43501Anyone202/cybermeowfia-termux
PoC-in-GitHub

Sources

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2026-05-21
Last Modified
2026-10-19
NVD status
Modified
MSRC Title
ipv6: rpl: reserve mac_len headroom when recompressed SRH grows

Frequently asked questions

What is CVE-2026-43501?

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.

Is CVE-2026-43501 actively exploited?

Active exploitation of CVE-2026-43501 has not been confirmed. Its EPSS score was 1.0% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-43501?

CVE-2026-43501 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Running Linux kernel? Hear about its next vulnerability

Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».

Get alerts for this productCISA KEV additions, October 2026Search CVEs

No credit card required · No monthly cap on website lookups · 250 API requests/month

Go further

Related vulnerabilities

Same product first, then the same vendor advisory and the same publication week.

Back to CVE Database