CVE-2025-21700 — Linux Vulnerability Details

What is CVE-2025-21700?

In the Linux kernel, the following vulnerability has been resolved: net: sched: Disallow replacing of child qdisc from one parent to another Lion Ackermann was able to create a UAF which can be abused for privilege escalation with the following script Step 1. create root qdisc tc qdisc add dev lo root handle 1:0 drr step2. a class for packet aggregation do demonstrate uaf tc class add dev lo classid 1:1 drr step3. a class for nesting tc class add dev lo classid 1:2 drr step4. a class to graft qdisc to tc class add dev lo classid 1:3 drr step5. tc qdisc add dev lo parent 1:1 handle 2:0 plug limit 1024 step6. tc qdisc add dev lo parent 1:2 handle 3:0 drr step7. tc class add dev lo classid 3:1 drr step 8. tc qdisc add dev lo parent 3:1 handle 4:0 pfifo step 9. Display the class/qdisc layout tc class ls dev lo class drr 1:1 root leaf 2: quantum 64Kb class drr 1:2 root leaf 3: quantum 64Kb class drr 3:1 root leaf 4: quantum 64Kb tc qdisc ls qdisc drr 1: dev lo root refcnt 2 qdisc plug 2: dev lo parent 1:1 qdisc pfifo 4: dev lo parent 3:1 limit 1000p qdisc drr 3: dev lo parent 1:2 step10. trigger the bug

The record classifies CVE-2025-21700 under weakness class CWE-416. Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 636 days ago.

Severity and exploitation probability

CVSS v3.1 base score: 7.8 — HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS (FIRST): 0.2% probability of exploitation in the next 30 days, higher than 14.1% of all scored CVEs
CISA KEV: Not listed in the CISA Known Exploited Vulnerabilities catalog
Threadlinqs priority: 6.5/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
Published: 2025-02-13

Is CVE-2025-21700 being exploited?

Weaponised exploit code for CVE-2025-21700 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. It currently carries a trending score of 5 in the Threadlinqs vulnerability feed.

trickest/cve (trickest)

Affected products and versions

Linux: Linux

How to fix CVE-2025-21700

The record marks a vendor fix as available for CVE-2025-21700. Patch reference: https://git.kernel.org/stable/c/38646749d6e12f9d80a08d21ca39f0beca20230d. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

Threat activity tracking CVE-2025-21700

1 tracked threat in the Threadlinqs corpus references CVE-2025-21700, either in the campaign’s CVE list or as an indicator on the campaign record.

Linux kernel net/sched action-IDR use-after-free LPE (CVE-2026-53264) and perf/aux page-UAF LPE (CVE-2026-64300) with public exploit — HIGH · 2026-11-11

Sources

Enriched from CVE.org, NVD, FIRST EPSS, public proof-of-concept repositories. This product uses the NVD API but is not endorsed or certified by the NVD.

Other references

Showing 5 of 8 recorded references.