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Linux CVE-2026-98021

| EUVDEUVD-2026-86674
2026-09-25 Linux GHSA-xp4j-cc89-xj49
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Monitor Track and reassess. Why: No CVSS yet + weak signal (CWE or non-zero EPSS).
Patch available 0.2% exploitation probability (EPSS)

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AnalysisCVE.org

In the Linux kernel, the following vulnerability has been resolved:

net: reject oversized tx_queue_len at netlink parse time

rtnl_create_link() assigns IFLA_TXQLEN directly to dev->tx_queue_len without going through netif_change_tx_queue_len(), so a device created with "ip link add ... txqueuelen 500000" bypasses the S16_MAX cap and still triggers the oversized ring allocations in pfifo_fast, tun and tap. The veth peer nest (rtnl_nla_parse_ifinfomsg()) and the RTM_NEWLINK-on-existing-device path reach the same sinks.

Enforce the cap in ifla_policy instead: IFLA_TXQLEN becomes NLA_POLICY_FULL_RANGE(NLA_U32, &txqlen_range) with txqlen_range = { .min = 0, .max = S16_MAX }. All netlink consumers parse against this policy - rtnl_setlink(), rtnl_newlink() (create and change), and the veth peer nest - so every netlink path is capped at parse time and rejects the attribute with -ERANGE plus a proper "integer out of range" extack message before any device state is modified (the RTM_SETLINK half-application wart is gone with it).

Document the bound in the rt-link.yaml netlink spec.

Conditions to recreate the bug:

  • CONFIG_NET_SCHED=y, CONFIG_VETH=y, CONFIG_USER_NS=y, CONFIG_NET_NS=y.
  • Unprivileged user in a fresh user+net namespace (unshare -Urn):

ip link add v0 txqueuelen 500000 type veth peer name v1 -> on the fixed kernel this is rejected with -ERANGE ("integer out of range" extack) instead of installing an oversized tx_queue_len that later inflates pfifo_fast/tun/tap ring allocations.

  • ip link set v0 txqueuelen 500000 is likewise rejected at parse time.

Affected VersionsENISA

Linux patch: 0
Linux patch: 7.2.7
Linux 2.6.23
Linux patch: 6.12.111
Linux 38f7b870d4a6a5d3ec21557e849620cb7d032965 <45ca9f59b6c7ea70e0a17054902b8a556913db34
Linux patch: 6.18.53
Linux 38f7b870d4a6a5d3ec21557e849620cb7d032965 <2fd0880f0272ec022906a05587fd91416ebecc38
Linux 38f7b870d4a6a5d3ec21557e849620cb7d032965 <1aa9e143bf51405665a793d4cc925e1c4f0c5922
Linux 38f7b870d4a6a5d3ec21557e849620cb7d032965 <a638a2625aa83160a394abe8e8b2e524a80c771b
Linux patch: 7.3-rc3

Affected Packages

euvd linux no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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Lifecycle Timeline

2
Patch available
Sep 25, 2026 - 11:02 EUVD
CVE Published
Sep 25, 2026 - 10:23 cve.org
UNKNOWN (no severity yet)

Threat Intelligence Overview

EPSS Score
0.2%
Top 94% exploitable
Data Quality
3 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity Not scored yet
CISA KEV No
Public POC No
EPSS 0.2%
Patch available Yes
Active threat No
Deciding rule
No CVSS yet + weak signal (CWE or non-zero EPSS)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

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