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CVE-2025-21806

CVSS base score: not scored

Vendor: Linux   Product: Linux

Description

In the Linux kernel, the following vulnerability has been resolved: net: let net.core.dev_weight always be non-zero The following problem was encountered during stability test: (NULL net_device): NAPI poll function process_backlog+0x0/0x530 \ returned 1, exceeding its budget of 0. ------------[ cut here ]------------ list_add double add: new=ffff88905f746f48, prev=ffff88905f746f48, \ next=ffff88905f746e40. WARNING: CPU: 18 PID: 5462 at lib/list_debug.c:35 \ __list_add_valid_or_report+0xf3/0x130 CPU: 18 UID: 0 PID: 5462 Comm: ping Kdump: loaded Not tainted 6.13.0-rc7+ RIP: 0010:__list_add_valid_or_report+0xf3/0x130 Call Trace: ? __warn+0xcd/0x250 ? __list_add_valid_or_report+0xf3/0x130 enqueue_to_backlog+0x923/0x1070 netif_rx_internal+0x92/0x2b0 __netif_rx+0x15/0x170 loopback_xmit+0x2ef/0x450 dev_hard_start_xmit+0x103/0x490 __dev_queue_xmit+0xeac/0x1950 ip_finish_output2+0x6cc/0x1620 ip_output+0x161/0x270 ip_push_pending_frames+0x155/0x1a0 raw_sendmsg+0xe13/0x1550 __sys_sendto+0x3bf/0x4e0 __x64_sys_sendto+0xdc/0x1b0 do_syscall_64+0x5b/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e The reproduction command is as follows: sysctl -w net.core.dev_weight=0 ping 127.0.0.1 This is because when the napi's weight is set to 0, process_backlog() may return 0 and clear the NAPI_STATE_SCHED bit of napi->state, causing this napi to be re-polled in net_rx_action() until __do_softirq() times out. Since the NAPI_STATE_SCHED bit has been cleared, napi_schedule_rps() can be retriggered in enqueue_to_backlog(), causing this issue. Making the napi's weight always non-zero solves this problem. Triggering this issue requires system-wide admin (setting is not namespaced).

Research & News Coverage

No mentions found in monitored research blogs or news feeds.

Referenced in Advisories

DateAdvisoryIssuer
2026-10-22 ICSA-26-295-16: Siemens SIMATIC S7-1500 TM MFP CISA
2025-03-13 ICSA-25-072-03: Siemens SIMATIC S7-1500 TM MFP CISA
2024-04-11 ICSA-24-102-01: Siemens SIMATIC S7-1500 TM MFP CISA

Lifecycle Timeline

Each milestone comes from a different source, so gaps between them are gaps in what those sources publish, not evidence that nothing happened. EPSS history for this CVE holds 4 points from 2026-11-05, tracked daily from 2026-11-05; earlier points are weekly, which dates a spike to within a week. Peak probability 0.2% on 2026-11-05.

Published Applicability

Red Hat CSAF/VEX 167 affected · 303 fixed · 0 not affected
OSV.dev (incl. GHSA) 15 affected · 15 fixed · 0 not affected
CVE List v5 (CNA container) 9 affected · 0 fixed · 9 not affected
CVE List v5 (ADP/Vulnrichment) 2 affected · 0 fixed · 0 not affected

Check whether a specific version is affected →

What each source publishes about which product versions carry this vulnerability, kept as written rather than merged. Absence here means no source has published applicability data, not that nothing is affected.

Detection & Exploitation

Exploit / Pen Test
none published
Network IDS/IPS
none published
Host / SIEM
none published

Coverage across public collections only: Nuclei and OpenVAS NVT (scan); Snort and Suricata ET Open (network); Sigma and YARA (host/SIEM); Metasploit, Exploit-DB, public GitHub repositories and NVD exploit references (exploit). Absence here means nothing public was found, not that detection is impossible.
GitHub PoC repositories are collected automatically by PoC-in-GitHub (CC0) and filtered to repositories that are still online, contain code, and are starred or at least two weeks old. They are still not vetted: some are fakes and some are malware. Treat them as evidence that code was published, not as code to run.
NVD exploit references are links NVD's analysts tag as exploits; they confirm an exploit was referenced but carry no date. This product uses data from the NVD but is not endorsed or certified by the NVD.
OpenVAS coverage derives from the Greenbone Community Feed, made available under the Open Database License (ODbL) v1.0; its individual Vulnerability Tests are licensed GNU GPL v2.

No exploit-tool sightings recorded for this CVE.

Metasploit is dated by the first commit of the module file, Exploit-DB by its publication date, and GitHub repositories by their creation date. GitHub PoC repositories are filtered (still online, contain code, starred or at least two weeks old) but not vetted: some are fakes and some are malware, so they show that code was published, not that it works or is safe to run. Evidence tiers are explained on the About page.

Distribution Status

Debian · linux bookworm 6.1.129-1 trixie 6.12.13-1 forky 6.12.13-1 sid 6.12.13-1 scope: local

Where the distribution has shipped a fix, and in which version. Green means the release has resolved it, amber that it is still open. Data from the Debian Security Tracker, used under Debian's MIT / GPLv2+ terms. Debian is upstream of several other distributions, so a fix here often precedes theirs.

CISA Assessment (Vulnrichment / SSVC)

No CISA Vulnrichment record for this CVE.

Federal Remediation Window (BOD 26-04)

No
no
total control
If the asset isRemediate withinTable 1 row
Publicly exposed 14 days 7 of 16
Not publicly exposed Fix on system upgrade 15 of 16

BOD 26-04 replaced the single KEV deadline of BOD 22-01 with four inputs: whether the asset is publicly exposed, KEV status, whether exploitation is automatable, and technical impact. Exposure belongs to each agency's asset, not to the CVE, so both outcomes are shown. Automatable and technical impact come from the CISA assessment above. Days are calendar days; for KEV entries the clock starts on the date it was added, and otherwise when the agency identifies the vulnerability on an asset. Assumed: Automatable not assessed — assumed no; Technical impact not assessed — assumed total, following CISA's defaults for missing data. Agencies make the final exposure call asset by asset, and may set shorter timelines.

External References