Critical

CVE-2026-89555 — mpls: reload header after pskb_may_pull()

In the Linux kernel, the following vulnerability has been resolved: mpls: reload header after pskb_may_pull() mpls_select_multipath() calls mpls_multipath_hash() to choose a nexthop when an MPLS route has multiple nexthops. While walking the MPLS label stack, the hash routine caches hdr for the current label. After finding the bottom-of-stack label, it calls pskb_may_pull() before reading the inner IP header. If an skb is constructed with the inner IP header in nonlinear data and insufficient tailroom in the linear head, pskb_may_pull() calls pskb_expand_head() to replace the skb head and free the old one. This leaves hdr pointing to freed memory. The IPv6 path can invalidate hdr again when it performs a second pull for the larger header. The issue was found through static analysis. A reproducer sending a legal Geneve packet through a bareudp/MPLS multipath setup triggered the same KASAN report in 2 of 2 unpatched runs: BUG: KASAN: slab-use-after-free in mpls_select_multipath Read of size 1 at addr ffff88800ecc6e20 by task ksoftirqd/1/23 Call Trace: mpls_select_multipath mpls_forward __netif_receive_skb_list_core netif_receive_skb_list_internal napi_complete_done gro_cell_poll __napi_poll net_rx_action Freed by task 23: kfree pskb_expand_head __pskb_pull_tail mpls_select_multipath Reload hdr from the current skb head after each successful pull before deriving the inner IPv4 or IPv6 header pointer.

Published Sep 11, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

Technical severity (critical)+10

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Linux

CVSS base

9.8

Critical · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 9f427a0e474a67b454420c131709600d44850486 and < aa4fe0b450a461aa1162fe8375f5d28f4c957df8≥ 9f427a0e474a67b454420c131709600d44850486 and < b1c0783b2facc398437ad8f8b86c636d7a78f8db≥ 9f427a0e474a67b454420c131709600d44850486 and < bfaaff99238326166694354a63a76c02563f98b1≥ 9f427a0e474a67b454420c131709600d44850486 and < d9640239827d6d0cb84263b590f7a4f1596c17eb≥ 9f427a0e474a67b454420c131709600d44850486 and < fed638a248116b8a249bd4202d28e5934bdc65ad≥ 9f427a0e474a67b454420c131709600d44850486 and < d82b90a38c2ca8a0694428eab0e9551c23f2447d≥ 9f427a0e474a67b454420c131709600d44850486 and < 49d38c1b4390412f8950d33dfaee0ccbd17beb81≥ 9f427a0e474a67b454420c131709600d44850486 and < 29e63b8d9fc150cc191b1c6eb7e16e1247e1b650 and 3 more version ad864d9fce0ec56cc8f6afe5c6a0e6d7f484b9eb≥ 4.9.8 and < 4.10version 4.10	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
9.8	CVSS 3.1	Critical	3.9	5.9	416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database
9.8	CVSS 3.1	Critical	—	—	Linux via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67)

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 15, 2026
CVSS changed · 9.8
Oct 15, 2026 · NIST National Vulnerability Database
Source status changed · → Received
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Sep 11, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

8 on the record

git.kernel.org/stable/c/d82b90a38c2ca8a0694428eab0e9551c23f2447d
NIST National Vulnerability Database
git.kernel.org/stable/c/49d38c1b4390412f8950d33dfaee0ccbd17beb81
NIST National Vulnerability Database
git.kernel.org/stable/c/aa4fe0b450a461aa1162fe8375f5d28f4c957df8
NIST National Vulnerability Database
git.kernel.org/stable/c/fed638a248116b8a249bd4202d28e5934bdc65ad
NIST National Vulnerability Database
git.kernel.org/stable/c/bfaaff99238326166694354a63a76c02563f98b1
NIST National Vulnerability Database
git.kernel.org/stable/c/b1c0783b2facc398437ad8f8b86c636d7a78f8db
NIST National Vulnerability Database
git.kernel.org/stable/c/29e63b8d9fc150cc191b1c6eb7e16e1247e1b650
NIST National Vulnerability Database
git.kernel.org/stable/c/d9640239827d6d0cb84263b590f7a4f1596c17eb
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 14h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 14h
Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No FIRST EPSS score.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-89555 is "mpls: reload header after pskb_may_pull()", rated Critical. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.8 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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