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CVE-2026-98234

Linux: net/sched: hhf: cap hh_flows_limit at change time

Linux LinuxOperating systems
Open in ThreatlineRecord JSON
CVSS
NoneNot scored
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.18%Chance of exploitation activity in the next 30 days, higher than 6% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in7adfd0a42174b85c6bd678858ecd6674f403f336Also 35fd423a5c5132c6f4321f6c4f0a7b4b90af830c, 06d2a101e89063cb0b9b459104db48bdfb0a797d and 2 moreCVE List
Published6 Oct 2026Updated 19 Oct 2026CVE List

What fixes it

  • 7adfd0a42174b85c6bd678858ecd6674f403f336LinuxCVE List
  • 35fd423a5c5132c6f4321f6c4f0a7b4b90af830cLinuxCVE List
  • 06d2a101e89063cb0b9b459104db48bdfb0a797dLinuxCVE List
  • 1731ff1d20489afe4cd01b7d16d37f324746ac54LinuxCVE List
  • 2cef2588c995722a901368def30befeef9ae55c6LinuxCVE List

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

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.

Text from CVE List

Affected versions 18

  • Linuxaffected: 10239edf86f137ce4c39b62ea9575e8053c549a0 before 7adfd0a42174b85c6bd678858ecd6674f403f336CVE List
  • Linuxaffected: 10239edf86f137ce4c39b62ea9575e8053c549a0 before 35fd423a5c5132c6f4321f6c4f0a7b4b90af830cCVE List
  • Linuxaffected: 10239edf86f137ce4c39b62ea9575e8053c549a0 before 06d2a101e89063cb0b9b459104db48bdfb0a797dCVE List
  • Linuxaffected: 10239edf86f137ce4c39b62ea9575e8053c549a0 before d8e2f1f0263b7c97b222c06070cccf13e0ab7112CVE List
  • Linuxaffected: 10239edf86f137ce4c39b62ea9575e8053c549a0 before f3f4a5cb4a6e9b1f1f25d34dfc25f836a1601db4CVE List
  • Linuxaffected: 10239edf86f137ce4c39b62ea9575e8053c549a0 before 1731ff1d20489afe4cd01b7d16d37f324746ac54CVE List
  • Linuxaffected: 10239edf86f137ce4c39b62ea9575e8053c549a0 before f6547d27ce2093c5627636fb63dd0b7523c466f9CVE List
  • Linuxaffected: 10239edf86f137ce4c39b62ea9575e8053c549a0 before 2cef2588c995722a901368def30befeef9ae55c6CVE List
  • Linuxaffected: 3.14CVE List
  • Linuxunaffected: all versions before 3.14CVE List
  • Linuxunaffected: 5.10.271 through 5.10.*CVE List
  • Linuxunaffected: 5.15.222 through 5.15.*CVE List
  • Linuxunaffected: 6.1.189 through 6.1.*CVE List
  • Linuxunaffected: 6.6.158 through 6.6.*CVE List
  • Linuxunaffected: 6.12.112 through 6.12.*CVE List
  • Linuxunaffected: 6.18.54 through 6.18.*CVE List
  • Linuxunaffected: 7.2.8 through 7.2.*CVE List
  • Linuxunaffected: 7.3CVE List

References 8