# CVE-2025-21700 — Linux > As of 2026-11-11, CVE-2025-21700 is a HIGH-severity vulnerability in Linux, CVSS v3.1 7.8, EPSS 0.2% (14.1th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2025-21700, most recently “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”. **Last updated:** 2026-11-11 ## 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](https://intel.threadlinqs.com/cwe/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](https://github.com/trickest/cve/blob/main/2025/CVE-2025-21700.md) (trickest) ## Affected products and versions - [Linux](https://intel.threadlinqs.com/vendors/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](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](https://intel.threadlinqs.com/threat/TL-2026-5729) — 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** - [git.kernel.org](https://git.kernel.org/stable/c/cd796e269123e1994bfc4e99dd76680ba0946a97) - [git.kernel.org (fe18c21d67dc7d1bcce1bba56515b1b0306db19b)](https://git.kernel.org/stable/c/fe18c21d67dc7d1bcce1bba56515b1b0306db19b) - [git.kernel.org (38646749d6e12f9d80a08d21ca39f0beca20230d)](https://git.kernel.org/stable/c/38646749d6e12f9d80a08d21ca39f0beca20230d) - [git.kernel.org (deda09c0543a66fa51554abc5ffd723d99b191bf)](https://git.kernel.org/stable/c/deda09c0543a66fa51554abc5ffd723d99b191bf) - [git.kernel.org (7e2bd8c13b07e29a247c023c7444df23f9a79fd8)](https://git.kernel.org/stable/c/7e2bd8c13b07e29a247c023c7444df23f9a79fd8) _Showing 5 of 8 recorded references._ Canonical: https://intel.threadlinqs.com/cve/CVE-2025-21700 Every threat comes with one complete detection in Splunk SPL, Microsoft KQL and Sigma, free for everyone; a free account adds daily TL Creds to unlock the rest. 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