CVE-2026-98234

Received Received - Intake

BaseFortify

Publication date: 2026-10-06

Last updated on: 2026-10-19

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: hhf: cap hh_flows_limit at change time hhf_change() stores TCA_HHF_HH_FLOWS_LIMIT with no upper bound. A huge hh_flows_limit lets each new heavy-hitter flow pass the hh_flows_current_cnt check in alloc_new_hh() and forces a fixed-size kzalloc(GFP_ATOMIC) per flow under spoofed traffic, for unbounded memory growth. Bound the attribute with NLA_POLICY_MAX() at 2*HH_FLOWS_CNT (the hhf_init() default) and report the rejected value via extack. The deprecated nested parse is kept: legacy tc does not set NLA_F_NESTED on TCA_OPTIONS. Configs relying on hh_limit above the default were relying on unbounded, unsafe behaviour and are not supported going forward. hhf_init() also ran hhf_change() before setting the default hh_flows_limit, so a user-supplied hh_limit at add time was clobbered back to 2048. Set the default before hhf_change() so the configured value sticks. This is a follow-up to commit eb56a495f59b ("net/sched: hhf: clamp quantum in change and init paths"), which bounded the quantum of the same qdisc; the hh_flows_limit bound is the remaining unbounded knob of that series' scope. Conditions to recreate the bug: CAP_NET_ADMIN in a user namespace; tc qdisc change dev X root hhf hh_limit 4294967295 succeeds and the value is echoed by tc qdisc show, unbounding heavy-hitter flow allocations; also tc qdisc add dev X root hhf hh_limit 500 stores 2048 instead of 500.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-10-06

Last Modified

2026-10-19

Generated

2026-10-19

AI Q&A

2026-10-06

EPSS Evaluated

2026-10-18

NVD

CVE-2026-98234

EUVD

EUVD-2026-93162

Affected Vendors & Products

Vendor	Product	Version / Range
Linux	Linux	10239edf86f137ce4c39b62ea9575e8053c549a0
Linux	Linux	10239edf86f137ce4c39b62ea9575e8053c549a0
Linux	Linux	10239edf86f137ce4c39b62ea9575e8053c549a0
Linux	Linux	10239edf86f137ce4c39b62ea9575e8053c549a0
Linux	Linux	10239edf86f137ce4c39b62ea9575e8053c549a0
Linux	Linux	10239edf86f137ce4c39b62ea9575e8053c549a0
Linux	Linux	10239edf86f137ce4c39b62ea9575e8053c549a0
Linux	Linux	10239edf86f137ce4c39b62ea9575e8053c549a0
Linux	Linux	3.14

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This is a Linux kernel vulnerability where the hh_flows_limit parameter in the HHF qdisc scheduler could be set to an extremely high value without proper bounds. This allows an attacker with CAP_NET_ADMIN privileges to trigger unbounded memory allocation by creating many heavy-hitter flows, leading to potential denial-of-service conditions.

Detection Guidance

This vulnerability can be detected by checking the hh_flows_limit value on traffic control (tc) qdisc configurations. Use 'tc qdisc show' to inspect hhf qdisc settings. If hh_limit is set to an unusually high value (e.g., 4294967295), it indicates potential exploitation. Also monitor memory usage spikes due to unbounded allocations.

Impact Analysis

If exploited, this flaw could cause system instability or crashes due to excessive memory consumption. It requires CAP_NET_ADMIN privileges in a user namespace, so unprivileged users cannot trigger it directly.

Compliance Impact

This vulnerability primarily impacts system resource management and could lead to denial-of-service conditions due to unbounded memory allocation under spoofed traffic. It does not directly affect compliance with GDPR, HIPAA, or similar standards as it is not a data breach or privacy violation. However, if exploited, it may cause system instability that could indirectly impact availability requirements in these regulations.

Mitigation Strategies

Immediately update the Linux kernel to a patched version. Remove or reset any hhf qdisc configurations with hh_limit values exceeding the default (2048). Restrict CAP_NET_ADMIN privileges in user namespaces to prevent unauthorized tc command execution.

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