Answer in brief
CVE-2025-21971 records a High severity (CVSS 7.8) vulnerability in net_sched: Prevent creation of classes with TC_H_ROOT. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:2.6.25:-:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:6.14:rc1:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:6.14:rc2:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:6.14:rc3:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:6.14:rc4:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:6.14:rc5:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:6.14:rc6:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=066a3b5b2346febf9a655b444567b7138e3bb939 <e05d9938b1b0ac40b6054cc5fa0ccbd9afd5ed4c || >=066a3b5b2346febf9a655b444567b7138e3bb939 <7a82fe67a9f4d7123d8e5ba8f0f0806c28695006 || >=066a3b5b2346febf9a655b444567b7138e3bb939 <003d92c91cdb5a64b25a9a74cb8543aac9a8bb48 || >=066a3b5b2346febf9a655b444567b7138e3bb939 <e5ee00607bbfc97ef1526ea95b6b2458ac9e7cb7 || >=066a3b5b2346febf9a655b444567b7138e3bb939 <78533c4a29ac3aeddce4b481770beaaa4f3bfb67 || >=066a3b5b2346febf9a655b444567b7138e3bb939 <5c3ca9cb48b51bd72bf76b8b05e24f3cd53db5e7 || >=066a3b5b2346febf9a655b444567b7138e3bb939 <94edfdfb9505ab608e86599d1d1e38c83816fc1c || >=066a3b5b2346febf9a655b444567b7138e3bb939 <0c3057a5a04d07120b3d0ec9c79568fceb9c921e | e05d9938b1b0ac40b6054cc5fa0ccbd9afd5ed4c, 7a82fe67a9f4d7123d8e5ba8f0f0806c28695006, 003d92c91cdb5a64b25a9a74cb8543aac9a8bb48, e5ee00607bbfc97ef1526ea95b6b2458ac9e7cb7, 78533c4a29ac3aeddce4b481770beaaa4f3bfb67, 5c3ca9cb48b51bd72bf76b8b05e24f3cd53db5e7, 94edfdfb9505ab608e86599d1d1e38c83816fc1c, 0c3057a5a04d07120b3d0ec9c79568fceb9c921e |
| Linux/Linuxgeneric | 2.6.25 | Not reported |
Published upstream
Apr 1, 2025
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 15, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
In the Linux kernel, the following vulnerability has been resolved: net_sched: Prevent creation of classes with TC_H_ROOT The function qdisc_tree_reduce_backlog() uses TC_H_ROOT as a termination condition when traversing up the qdisc tree to update parent backlog counters. However, if a class is created with classid TC_H_ROOT, the traversal terminates prematurely at this class instead of reaching the actual root qdisc, causing parent statistics to be incorrectly maintained. In case of DRR, this could lead to a crash as reported by Mingi Cho. Prevent the creation of any Qdisc class with classid TC_H_ROOT (0xFFFFFFFF) across all qdisc types, as suggested by Jamal.
Quoted source text, attributed separately from HOL analysis.