Vulnerability in Linux kernel (CVE-2026-89561)
Summary
Vulnerability in Linux kernel (CVE-2026-89561). Risk of unauthorized operations or information disclosure.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()
ipv6_rpl_srh_rcv() dereferences idev from __in6_dev_get() without a NULL
check when reading idev->cnf.rpl_seg_enabled.
When the device's MTU drops below IPV6_MIN_MTU, addrconf_ifdown() clears
dev->ip6_ptr through RCU_INIT_POINTER(). A packet that passed the idev
check in ip6_rcv_core() can then reach ipv6_rpl_srh_rcv() with
dev->ip6_ptr already NULL.
Reproduced by flooding the receiving interface with ping6 traffic while
flapping its MTU between 1500 and 1200:
BUG: KASAN: null-ptr-deref in ipv6_rpl_srh_rcv+0xb3/0x1070
Read of size 4 at addr 00000000000006b4 by task ping6/394
CPU: 2 UID: 0 PID: 394 Comm: ping6 Not tainted 7.2.0-rc7-micro-vm-dev-00095-g24ef02f934ee #240 PREEMPT(full)
Call Trace:
kasan_report+0xc6/0x100
ipv6_rpl_srh_rcv+0xb3/0x1070
ip6_protocol_deliver_rcu+0x759/0x9a0
ip6_input_finish+0xa8/0x1b0
ip6_input+0xe1/0x490
ipv6_rcv+0x33d/0x460
__netif_receive_skb_one_core+0xd6/0x130
process_backlog+0x2cc/0xa00
__napi_poll.constprop.0+0x56/0x270
net_rx_action+0x327/0x730
handle_softirqs+0x11e/0x630
do_softirq+0xb3/0xf0
Both ipv6_rpl_srh_rcv() and ipv6_srh_rcv() are called only from
ipv6_rthdr_rcv(), which already has an idev lookup.
Fix the NULL dereference on the RPL path by checking idev in
ipv6_rthdr_rcv(), before it calls either function. The callees take idev as
an argument and no longer call __i…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-89561 has been found in Linux kernel.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-89561" on the vendor's site.
CVE-2026-89561 (Linux kernel) — CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (unclassified) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
References
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web nvd.nist.gov
- web github.com