CVE-2025-21702: pfifo_tail_enqueue: Drop new packet when sch->limit == 0
Noroxi assessment
Priority: Monitor (action score 28/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.28% (FIRST EPSS).
- Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
- Fixed version: Linux Linux 020ecb76812a0526f4130ab5aeb6dc7c773e7ab9, 647cef20e649c576dff271e018d5d15d998b629d, 78285b53266d6d51fa4ff504a23df03852eba84e.
Low priority for now. Upgrade to Linux Linux 020ecb76812a0526f4130ab5aeb6dc7c773e7ab9, 647cef20e649c576dff271e018d5d15d998b629d, 78285b53266d6d51fa4ff504a23df03852eba84e or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
In 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.
- BDU:2025-02167
- SUSE-SU-2025:01965-1
- SUSE-SU-2025:02000-1
- SUSE-SU-2025:02099-1
- SUSE-SU-2025:02601-1
- SUSE-SU-2025:02602-1
- SUSE-SU-2025:02604-1
- SUSE-SU-2025:02606-1
- SUSE-SU-2025:02607-1
- SUSE-SU-2025:02608-1
- SUSE-SU-2025:02610-1
- SUSE-SU-2025:02611-1
- SUSE-SU-2025:02618-1
- SUSE-SU-2025:02619-1
- SUSE-SU-2025:02627-1
- SUSE-SU-2025:02632-1
- SUSE-SU-2025:02636-1
- SUSE-SU-2025:02637-1
- SUSE-SU-2025:02638-1
- SUSE-SU-2025:02647-1
- Published
- Feb 18, 2025
- Updated
- Oct 15, 2026
- EPSS
- 0.2% · 20th percentile
- CWE
- —
Report tools
Action score
28
Monitor
Low priority for now.
- CVSS
- 28 / 40 · 7.0 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
CNA vs NVD score
- NVD
- 7.0
- CNA · Linux
- 7.8
- 0.8 point gap
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
Running WordPress? Scan your site free with WP Lens
Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| linux | linux kernel | cpe:2.3:o:linux:linux_kernel |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- linux linux kernel2.6.34 and later · before 5.4.291
- linux linux kernel5.5 and later · before 5.10.235
- linux linux kernel5.11 and later · before 5.15.179
- linux linux kernel5.16 and later · before 6.1.130
- linux linux kernel6.2 and later · before 6.6.83
- linux linux kernel6.7 and later · before 6.12.14
- linux linux kernel6.13 and later · before 6.13.3
- linux linux kernel6.14
Versions reported by the vendor
Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.
Linux Linux
- 2.6.34affected
- 57dbb2d83d100ea601c54fe129bfde0678db5dee and later · before 78285b53266d6d51fa4ff504a23df03852eba84eaffected · git
- 57dbb2d83d100ea601c54fe129bfde0678db5dee and later · before 7a9723ec27aff5674f1fd4934608937f1d650980affected · git
- 57dbb2d83d100ea601c54fe129bfde0678db5dee and later · before a56a6e8589a9b98d8171611fbcc1e45a15fd2455affected · git
- 57dbb2d83d100ea601c54fe129bfde0678db5dee and later · before 020ecb76812a0526f4130ab5aeb6dc7c773e7ab9affected · git
- 57dbb2d83d100ea601c54fe129bfde0678db5dee and later · before 79a955ea4a2e5ddf4a36328959de0de496419888affected · git
- 57dbb2d83d100ea601c54fe129bfde0678db5dee and later · before e40cb34b7f247fe2e366fd192700d1b4f38196caaffected · git
- 57dbb2d83d100ea601c54fe129bfde0678db5dee and later · before b6a079c3b6f95378f26e2aeda520cb3176f7067baffected · git
- 57dbb2d83d100ea601c54fe129bfde0678db5dee and later · before 647cef20e649c576dff271e018d5d15d998b629daffected · git
- before 2.6.34not affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | linux | before 6.1.133-1 | 6.1.133-1 |
| Debian:13 | linux | before 6.12.15-1 | 6.12.15-1 |
| openSUSE:Leap 15.6 | dtb-aarch64 | before 6.4.0-150600.23.53.1 | 6.4.0-150600.23.53.1 |
| openSUSE:Leap 15.6 | kernel-64kb | before 6.4.0-150600.23.53.1 | 6.4.0-150600.23.53.1 |
| openSUSE:Leap 15.6 | kernel-azure | before 6.4.0-150600.8.40.1 | 6.4.0-150600.8.40.1 |
| openSUSE:Leap 15.6 | kernel-debug | before 6.4.0-150600.23.53.1 | 6.4.0-150600.23.53.1 |
| openSUSE:Leap 15.6 | kernel-default | before 6.4.0-150600.23.53.1 | 6.4.0-150600.23.53.1 |
| openSUSE:Leap 15.6 | kernel-default-base | before 6.4.0-150600.23.53.1.150600.12.24.1 | 6.4.0-150600.23.53.1.150600.12.24.1 |
| openSUSE:Leap 15.6 | kernel-docs | before 6.4.0-150600.23.53.1 | 6.4.0-150600.23.53.1 |
| openSUSE:Leap 15.6 | kernel-kvmsmall | before 6.4.0-150600.23.53.1 | 6.4.0-150600.23.53.1 |
| openSUSE:Leap 15.6 | kernel-obs-build | before 6.4.0-150600.23.53.1 | 6.4.0-150600.23.53.1 |
| openSUSE:Leap 15.6 | kernel-obs-qa | before 6.4.0-150600.23.53.1 | 6.4.0-150600.23.53.1 |
| openSUSE:Leap 15.6 | kernel-source | before 6.4.0-150600.23.53.1 | 6.4.0-150600.23.53.1 |
| openSUSE:Leap 15.6 | kernel-source-azure | before 6.4.0-150600.8.40.1 | 6.4.0-150600.8.40.1 |
| openSUSE:Leap 15.6 | kernel-syms | before 6.4.0-150600.23.53.1 | 6.4.0-150600.23.53.1 |
| openSUSE:Leap 15.6 | kernel-syms-azure | before 6.4.0-150600.8.40.1 | 6.4.0-150600.8.40.1 |
| openSUSE:Leap 15.6 | kernel-zfcpdump | before 6.4.0-150600.23.53.1 | 6.4.0-150600.23.53.1 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_58 | before 15-2.1 | 15-2.1 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_60 | before 13-2.1 | 13-2.1 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_61 | before 12-2.1 | 12-2.1 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_64 | before 7-2.1 | 7-2.1 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_66 | before 5-2.1 | 5-2.1 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_68 | before 2-2.1 | 2-2.1 |
| SUSE:Linux Enterprise Live Patching 15 SP3 | kernel-livepatch-SLE15-SP3_Update_46 | before 17-150300.2.1 | 17-150300.2.1 |
+72
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV90Now
- CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV89Now
- CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV85Now
Published before and after this one in the same product
- ← EarlierCVE-2025-21701Feb 13, 2025 · net: avoid race between device unregistration and ethnl ops18Monitor
- ← EarlierCVE-2025-21700Feb 13, 2025 · net: sched: Disallow replacing of child qdisc from one parent to another31Monitor
- Later →CVE-2025-21703Feb 18, 2025 · netem: Update sch->q.qlen before qdisc_tree_reduce_backlog()31Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Linux Linux | 020ecb76812a0526f4130ab5aeb6dc7c773e7ab9 | Vendor (CNA) |
| Linux Linux | 647cef20e649c576dff271e018d5d15d998b629d | Vendor (CNA) |
| Linux Linux | 78285b53266d6d51fa4ff504a23df03852eba84e | Vendor (CNA) |
| Linux Linux | 79a955ea4a2e5ddf4a36328959de0de496419888 | Vendor (CNA) |
| Linux Linux | 7a9723ec27aff5674f1fd4934608937f1d650980 | Vendor (CNA) |
| Linux Linux | a56a6e8589a9b98d8171611fbcc1e45a15fd2455 | Vendor (CNA) |
| Linux Linux | b6a079c3b6f95378f26e2aeda520cb3176f7067b | Vendor (CNA) |
| Linux Linux | e40cb34b7f247fe2e366fd192700d1b4f38196ca | Vendor (CNA) |
| debian:linux | 6.1.133-1 · Debian:12 | Package registry (OSV) |
| opensuse:dtb-aarch64 | 6.4.0-150600.23.53.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:kernel-64kb | 6.4.0-150600.23.53.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:kernel-azure | 6.4.0-150600.8.40.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:kernel-debug | 6.4.0-150600.23.53.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:kernel-default | 6.4.0-150600.23.53.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:kernel-default-base | 6.4.0-150600.23.53.1.150600.12.24.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:kernel-docs | 6.4.0-150600.23.53.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:kernel-kvmsmall | 6.4.0-150600.23.53.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:kernel-obs-build | 6.4.0-150600.23.53.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:kernel-obs-qa | 6.4.0-150600.23.53.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:kernel-source-azure | 6.4.0-150600.8.40.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:kernel-syms-azure | 6.4.0-150600.8.40.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| suse:kernel-64kb | 6.4.0-150600.23.53.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP6 | Package registry (OSV) |
| suse:kernel-azure | 6.4.0-150600.8.40.1 · SUSE:Linux Enterprise Module for Public Cloud 15 SP6 | Package registry (OSV) |
| suse:kernel-default | 6.4.0-150600.23.53.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP6 | Package registry (OSV) |
| suse:kernel-default-base | 6.4.0-150600.23.53.1.150600.12.24.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP6 | Package registry (OSV) |
| suse:kernel-docs | 6.4.0-150600.23.53.1 · SUSE:Linux Enterprise Module for Development Tools 15 SP6 | Package registry (OSV) |
| suse:kernel-livepatch-SLE15-SP6_Update_12 | 1-150600.13.3.1 · SUSE:Linux Enterprise Live Patching 15 SP6 | Package registry (OSV) |
| suse:kernel-obs-build | 6.4.0-150600.23.53.1 · SUSE:Linux Enterprise Module for Development Tools 15 SP6 | Package registry (OSV) |
| suse:kernel-source | 6.4.0-150600.23.53.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP6 | Package registry (OSV) |
| suse:kernel-source-azure | 6.4.0-150600.8.40.1 · SUSE:Linux Enterprise Module for Public Cloud 15 SP6 | Package registry (OSV) |
+3
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- A low-privileged account is enough.
- No user action is required.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Local
- Attack complexity
- High
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
—
CVSS vector
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (13 more)Show less
- git.kernel.org/stable/c/647cef20e649c576dff271e018d5d15d998b629d
- git.kernel.org/stable/c/78285b53266d6d51fa4ff504a23df03852eba84e
- git.kernel.org/stable/c/79a955ea4a2e5ddf4a36328959de0de496419888
- git.kernel.org/stable/c/7a9723ec27aff5674f1fd4934608937f1d650980
- git.kernel.org/stable/c/a56a6e8589a9b98d8171611fbcc1e45a15fd2455
- git.kernel.org/stable/c/b6a079c3b6f95378f26e2aeda520cb3176f7067b
- git.kernel.org/stable/c/e40cb34b7f247fe2e366fd192700d1b4f38196ca
- lists.debian.org/debian-lts-announce/2025/05/msg00030.html
- lists.debian.org/debian-lts-announce/2025/05/msg00045.html
- cert-portal.siemens.com/productcert/html/ssa-019113.html
- cert-portal.siemens.com/productcert/html/ssa-082556.html
- cert-portal.siemens.com/productcert/html/ssa-457936.html
- cert-portal.siemens.com/productcert/html/ssa-784472.html
Vendor advisories and official records. Exploit/PoC links are deliberately left out.