CVE-2025-39894: netfilter: br_netfilter: do not check confirmed bit in br_nf_local_in() after confirm
Noroxi assessment
Priority: Monitor (action score 22/100)
- 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: 0.33% (FIRST EPSS).
- Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
- According to CISA the attack is automatable: targets can be found by mass scanning.
- Fixed version: Linux Linux 479a54ab92087318514c82428a87af2d7af1a576, 5.15.192, 50db11e2bbb635e38e3dd096215580d6adb41fb0; cbl2 kernel 5.15.186.1-1 on CBL Mariner 2.0 5.15.200.1-1.
- Severity is disputed: the assigning authority (CNA) scores it 7.5, NVD 5.5.
Low priority for now. Upgrade to Linux Linux 479a54ab92087318514c82428a87af2d7af1a576, 5.15.192, 50db11e2bbb635e38e3dd096215580d6adb41fb0; cbl2 kernel 5.15.186.1-1 on CBL Mariner 2.0 5.15.200.1-1 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: netfilter: br_netfilter: do not check confirmed bit in br_nf_local_in() after confirm When send a broadcast packet to a tap device, which was added to a bridge, br_nf_local_in() is called to confirm the conntrack. If another conntrack with the same hash value is added to the hash table, which can be triggered by a normal packet to a non-bridge device, the below warning may happen. ------------[ cut here ]------------ WARNING: CPU: 1 PID: 96 at net/bridge/br_netfilter_hooks.c:632 br_nf_local_in+0x168/0x200 CPU: 1 UID: 0 PID: 96 Comm: tap_send Not tainted 6.17.0-rc2-dirty #44 PREEMPT(voluntary) RIP: 0010:br_nf_local_in+0x168/0x200 Call Trace: <TASK> nf_hook_slow+0x3e/0xf0 br_pass_frame_up+0x103/0x180 br_handle_frame_finish+0x2de/0x5b0 br_nf_hook_thresh+0xc0/0x120 br_nf_pre_routing_finish+0x168/0x3a0 br_nf_pre_routing+0x237/0x5e0 br_handle_frame+0x1ec/0x3c0 __netif_receive_skb_core+0x225/0x1210 __netif_receive_skb_one_core+0x37/0xa0 netif_receive_skb+0x36/0x160 tun_get_user+0xa54/0x10c0 tun_chr_write_iter+0x65/0xb0 vfs_write+0x305/0x410 ksys_write+0x60/0xd0 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> ---[ end trace 0000000000000000 ]--- To solve the hash conflict, nf_ct_resolve_clash() try to merge the conntracks, and update skb->_nfct. However, br_nf_local_in() still use the old ct from local variable 'nfct' after confirm(), which leads to this warning. If confirm() does not insert the conntrack entry and return NF_DROP, the warning may also occur. There is no need to reserve the WARN_ON_ONCE, just remove it.
- Published
- Oct 1, 2025
- Updated
- Oct 19, 2026
- EPSS
- 0.3% · 26th percentile
- CWE
- —
Report tools
Action score
22
Monitor
Low priority for now.
- CVSS
- 22 / 40 · 5.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.3%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 5.5
- CNA · Linux
- 7.5
- 2.0 point gap
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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.
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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 |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- debian debian linux11.0
- linux linux kernel6.1.81 and later · before 6.1.151
- linux linux kernel6.6.21 and later · before 6.6.105
- linux linux kernel6.7.9 and later · before 6.8
- linux linux kernel5.15.151 and later · before 5.15.192
- linux linux kernel6.13 and later · before 6.16.6
- linux linux kernel6.8.1 and later · before 6.12.46
- linux linux kernel6.17
- linux linux kernel6.8
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
- cb734975b0ffa688ff6cc0eed463865bf07b6c01, 6.8affected
- 7c3f28599652acf431a2211168de4a583f30b6d5 and later · before d00c8b0daf56012f69075e3377da67878c775e4caffected · git
- 2b1414d5e94e477edff1d2c79030f1d742625ea0 and later · before ccbad4803225eafe0175d3cb19f0d8d73b504a94affected · git
- 80cd0487f630b5382734997c3e5e3003a77db315 and later · before 50db11e2bbb635e38e3dd096215580d6adb41fb0affected · git
- 62e7151ae3eb465e0ab52a20c941ff33bb6332e9 and later · before c47ca77fee9071aa543bae592dd2a384f895c8b6affected · git
- 62e7151ae3eb465e0ab52a20c941ff33bb6332e9 and later · before a74abcf0f09f59daeecf7a3ba9c1d690808b0afeaffected · git
- 62e7151ae3eb465e0ab52a20c941ff33bb6332e9 and later · before 479a54ab92087318514c82428a87af2d7af1a576affected · git
- 5.15.151 and later · before 5.15.192affected · semver
- 6.1.81 and later · before 6.1.151affected · semver
- 6.6.21 and later · before 6.6.105affected · 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 6.1.153-1 | 6.1.153-1 |
| Debian:13 | linux | before 6.12.48-1 | 6.12.48-1 |
| Debian:14 | linux | before 6.16.6-1 | 6.16.6-1 |
| openSUSE:Leap 16.0 | dtb-aarch64 | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| openSUSE:Leap 16.0 | kernel-64kb | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| openSUSE:Leap 16.0 | kernel-azure | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| openSUSE:Leap 16.0 | kernel-default | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| openSUSE:Leap 16.0 | kernel-default-base | before 6.12.0-160000.36.1.160000.2.17 | 6.12.0-160000.36.1.160000.2.17 |
| openSUSE:Leap 16.0 | kernel-docs | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| openSUSE:Leap 16.0 | kernel-kvmsmall | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| openSUSE:Leap 16.0 | kernel-obs-build | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| openSUSE:Leap 16.0 | kernel-obs-qa | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| openSUSE:Leap 16.0 | kernel-rt | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| openSUSE:Leap 16.0 | kernel-source | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| openSUSE:Leap 16.0 | kernel-syms | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| openSUSE:Leap 16.0 | kernel-zfcpdump | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| SUSE:Linux Enterprise Server 16.0 | kernel-azure | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| SUSE:Linux Enterprise Server 16.0 | kernel-docs | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| SUSE:Linux Enterprise Server 16.0 | kernel-kvmsmall | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| SUSE:Linux Enterprise Server 16.0 | kernel-obs-qa | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| SUSE:Linux Enterprise Server 16.0 | kernel-zfcpdump | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| SUSE:Linux Micro 6.2 | kernel-64kb | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| SUSE:Linux Micro 6.2 | kernel-default | before 6.12.0-160000.36.1 | 6.12.0-160000.36.1 |
| SUSE:Linux Micro 6.2 | kernel-default-base | before 6.12.0-160000.36.1.160000.2.17 | 6.12.0-160000.36.1.160000.2.17 |
+4
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-2021-4460Oct 1, 2025 · drm/amdkfd: Fix UBSAN shift-out-of-bounds warning28Monitor
- ← EarlierCVE-2025-39893Oct 1, 2025 · spi: spi-qpic-snand: unregister ECC engine on probe error and device remove22Monitor
- Later →CVE-2025-39895Oct 1, 2025 · sched: Fix sched_numa_find_nth_cpu() if mask offline22Monitor
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 | 479a54ab92087318514c82428a87af2d7af1a576 | Vendor (CNA) |
| Linux Linux | 5.15.192 | Vendor (CNA) |
| Linux Linux | 50db11e2bbb635e38e3dd096215580d6adb41fb0 | Vendor (CNA) |
| Linux Linux | 6.1.151 | Vendor (CNA) |
| Linux Linux | 6.6.105 | Vendor (CNA) |
| Linux Linux | 6.8 | Vendor (CNA) |
| Linux Linux | a74abcf0f09f59daeecf7a3ba9c1d690808b0afe | Vendor (CNA) |
| Linux Linux | c47ca77fee9071aa543bae592dd2a384f895c8b6 | Vendor (CNA) |
| Linux Linux | ccbad4803225eafe0175d3cb19f0d8d73b504a94 | Vendor (CNA) |
| Linux Linux | d00c8b0daf56012f69075e3377da67878c775e4c | Vendor (CNA) |
| cbl2 kernel 5.15.186.1-1 on CBL Mariner 2.0 | 5.15.200.1-1 · CBL-Mariner Releases | Microsoft (MSRC) |
| debian:linux | 6.1.153-1 · Debian:12 | Package registry (OSV) |
| opensuse:dtb-aarch64 | 6.12.0-160000.36.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-64kb | 6.12.0-160000.36.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-azure | 6.12.0-160000.36.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-default | 6.12.0-160000.36.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-default-base | 6.12.0-160000.36.1.160000.2.17 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-docs | 6.12.0-160000.36.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-kvmsmall | 6.12.0-160000.36.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-obs-build | 6.12.0-160000.36.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-obs-qa | 6.12.0-160000.36.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-rt | 6.12.0-160000.36.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-source | 6.12.0-160000.36.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-syms | 6.12.0-160000.36.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| suse:kernel-64kb | 6.12.0-160000.36.1 · SUSE:Linux Micro 6.2 | Package registry (OSV) |
| suse:kernel-azure | 6.12.0-160000.36.1 · SUSE:Linux Enterprise Server 16.0 | Package registry (OSV) |
| suse:kernel-default | 6.12.0-160000.36.1 · SUSE:Linux Micro 6.2 | Package registry (OSV) |
| suse:kernel-default-base | 6.12.0-160000.36.1.160000.2.17 · SUSE:Linux Micro 6.2 | Package registry (OSV) |
| suse:kernel-docs | 6.12.0-160000.36.1 · SUSE:Linux Enterprise Server 16.0 | Package registry (OSV) |
| suse:kernel-kvmsmall | 6.12.0-160000.36.1 · SUSE:Linux Enterprise Server 16.0 | Package registry (OSV) |
+6
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.
No history yet (it accumulates with the daily EPSS job).
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.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
—
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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
- SSVC exploitation— → none
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (6 more)Show less
- git.kernel.org/stable/c/50db11e2bbb635e38e3dd096215580d6adb41fb0
- git.kernel.org/stable/c/a74abcf0f09f59daeecf7a3ba9c1d690808b0afe
- git.kernel.org/stable/c/c47ca77fee9071aa543bae592dd2a384f895c8b6
- git.kernel.org/stable/c/ccbad4803225eafe0175d3cb19f0d8d73b504a94
- git.kernel.org/stable/c/d00c8b0daf56012f69075e3377da67878c775e4c
- lists.debian.org/debian-lts-announce/2025/10/msg00008.html
Vendor advisories and official records. Exploit/PoC links are deliberately left out.