pfifo_tail_enqueue: Drop new packet when sch->limit == 0

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2025-21702
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-02-18 15:15:18 UTC
Updated2026-07-14 13:17:20 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: pfifo_tail_enqueue: Drop new packet when sch->limit == 0 Expected behaviour: In case we reach scheduler's limit, pfifo_tail_enqueue() will drop a packet in scheduler's queue and decrease scheduler's qlen by one. Then, pfifo_tail_enqueue() enqueue new packet and increase scheduler's qlen by one. Finally, pfifo_tail_enqueue() return `NET_XMIT_CN` status code. Weird behaviour: In case we set `sch->limit == 0` and trigger pfifo_tail_enqueue() on a scheduler that has no packet, the 'drop a packet' step will do nothing. This means the scheduler's qlen still has value equal 0. Then, we continue to enqueue new packet and increase scheduler's qlen by one. In summary, we can leverage pfifo_tail_enqueue() to increase qlen by one and return `NET_XMIT_CN` status code. The problem is: Let's say we have two qdiscs: Qdisc_A and Qdisc_B. - Qdisc_A's type must have '->graft()' function to create parent/child relationship. Let's say Qdisc_A's type is `hfsc`. Enqueue packet to this qdisc will trigger `hfsc_enqueue`. - Qdisc_B's type is pfifo_head_drop. Enqueue packet to this qdisc will trigger `pfifo_tail_enqueue`. - Qdisc_B is configured to have `sch->limit == 0`. - Qdisc_A is configured to route the enqueued's packet to Qdisc_B. Enqueue packet through Qdisc_A will lead to: - hfsc_enqueue(Qdisc_A) -> pfifo_tail_enqueue(Qdisc_B) - Qdisc_B->q.qlen += 1 - pfifo_tail_enqueue() return `NET_XMIT_CN` - hfsc_enqueue() check for `NET_XMIT_SUCCESS` and see `NET_XMIT_CN` => hfsc_enqueue() don't increase qlen of Qdisc_A. The whole process lead to a situation where Qdisc_A->q.qlen == 0 and Qdisc_B->q.qlen == 1. Replace 'hfsc' with other type (for example: 'drr') still lead to the same problem. This violate the design where parent's qlen should equal to the sum of its childrens'qlen. Bug impact: This issue can be used for user->kernel privilege escalation when it is reachable.

Risk And Classification

Primary CVSS: v3.1 7 HIGH from [email protected]

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Problem Types: NVD-CWE-noinfo

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary7HIGHCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 57dbb2d83d100ea601c54fe129bfde0678db5dee 78285b53266d6d51fa4ff504a23df03852eba84e git Not specified
CNA Linux Linux affected 57dbb2d83d100ea601c54fe129bfde0678db5dee 7a9723ec27aff5674f1fd4934608937f1d650980 git Not specified
CNA Linux Linux affected 57dbb2d83d100ea601c54fe129bfde0678db5dee a56a6e8589a9b98d8171611fbcc1e45a15fd2455 git Not specified
CNA Linux Linux affected 57dbb2d83d100ea601c54fe129bfde0678db5dee 020ecb76812a0526f4130ab5aeb6dc7c773e7ab9 git Not specified
CNA Linux Linux affected 57dbb2d83d100ea601c54fe129bfde0678db5dee 79a955ea4a2e5ddf4a36328959de0de496419888 git Not specified
CNA Linux Linux affected 57dbb2d83d100ea601c54fe129bfde0678db5dee e40cb34b7f247fe2e366fd192700d1b4f38196ca git Not specified
CNA Linux Linux affected 57dbb2d83d100ea601c54fe129bfde0678db5dee b6a079c3b6f95378f26e2aeda520cb3176f7067b git Not specified
CNA Linux Linux affected 57dbb2d83d100ea601c54fe129bfde0678db5dee 647cef20e649c576dff271e018d5d15d998b629d git Not specified
CNA Linux Linux affected 2.6.34 Not specified
CNA Linux Linux unaffected 2.6.34 semver Not specified
CNA Linux Linux unaffected 5.4.291 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.235 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.179 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.130 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.83 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.14 6.12.* semver Not specified
CNA Linux Linux unaffected 6.13.3 6.13.* semver Not specified
CNA Linux Linux unaffected 6.14 * original_commit_for_fix Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.6 * custom Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/b6a079c3b6f95378f26e2aeda520cb3176f7067b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/05/msg00030.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
git.kernel.org/stable/c/e40cb34b7f247fe2e366fd192700d1b4f38196ca 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/79a955ea4a2e5ddf4a36328959de0de496419888 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
cert-portal.siemens.com/productcert/html/ssa-082556.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
cert-portal.siemens.com/productcert/html/ssa-019113.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/7a9723ec27aff5674f1fd4934608937f1d650980 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/a56a6e8589a9b98d8171611fbcc1e45a15fd2455 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/05/msg00045.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
git.kernel.org/stable/c/78285b53266d6d51fa4ff504a23df03852eba84e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/647cef20e649c576dff271e018d5d15d998b629d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/020ecb76812a0526f4130ab5aeb6dc7c773e7ab9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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