CVE-2025-38177: Linux kernel · sch_hfsc: make hfsc_qlen_notify() idempotent
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High · fixed in 4.4.0-1145.151 : patch Linux kernel soon.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 4.4.0-1145.151, 4.15.0-1190.205~14.04.1, 4.4.0-270.304~14.04.1 +108
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 4 Jul 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-7653-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7655-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7665-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7671-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7671-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7671-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7686-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7712-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7712-2 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-aws-6.14pkg:deb/ubuntu/linux-aws-6.14?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
In the Linux kernel, the following vulnerability has been resolved: sch_hfsc: make hfsc_qlen_notify() idempotent hfsc_qlen_notify() is not idempotent either and not friendly to its callers, like fq_codel_dequeue(). Let's make it idempotent to ease qdisc_tree_reduce_backlog() callers' life: 1. update_vf() decreases cl->cl_nactive, so we can check whether it is non-zero before calling it. 2. eltree_remove() always removes RB node cl->el_node, but we can use RB_EMPTY_NODE() + RB_CLEAR_NODE() to make it safe.
References
- ubuntu.com/security/CVE-2025-38177 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-38177 (opens in a new tab)
- git.kernel.org/linus/51eb3b65544c9efd6a1026889ee5fb5aa62da3bb (opens in a new tab)
- git.kernel.org/stable/c/0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87 (opens in a new tab)
- git.kernel.org/stable/c/51eb3b65544c9efd6a1026889ee5fb5aa62da3bb (opens in a new tab)
- git.kernel.org/stable/c/9030a91235ae4845ec71902c3e0cecfc9ed1f2df (opens in a new tab)
- git.kernel.org/stable/c/c1175c4ad01dbc9c979d099861fa90a754f72059 (opens in a new tab)
- git.kernel.org/stable/c/d06476714d2819b550e0cc39222347e2c8941c9d (opens in a new tab)
- ubuntu.com/security/notices/USN-7653-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7655-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7665-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7671-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7671-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7671-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7686-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7712-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7712-2 (opens in a new tab)