CVE-2025-39802Network attack vector

System crash via unchecked no-SIMD Poly1305 execution

Published Sep 15, 2025 · Updated Sep 15, 2025

Improper SIMD-state handling in Linux 6.16 through 6.16.3 allows remote attackers to crash 32-bit ARM systems through Poly1305 traffic. The ARM poly1305_blocks_arch() path enters NEON processing without checking may_use_simd(), so kernel_neon_begin() triggers a fatal BUG when IRQ state forbids SIMD. Unauthenticated packets processed by WireGuard, IPsec ESP, or kTLS can reach the path, and repeated traffic can cause repeated kernel panics.

CVSS severity7.5
High
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper SIMD-state handling in Linux 6.16 through 6.16.3 allows remote attackers to crash 32-bit ARM systems through Poly1305 traffic. The ARM poly1305_blocks_arch() path enters NEON processing without checking may_use_simd(), so kernel_neon_begin() triggers a fatal BUG when IRQ state forbids SIMD. Unauthenticated packets processed by WireGuard, IPsec ESP, or kTLS can reach the path, and repeated traffic can cause repeated kernel panics.

The record

CVE
CVE-2025-39802
Published
Sep 15, 2025
Updated
Sep 15, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 15, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 15, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.16
  2. Affected versionversion=773426f4771bdd82ac5c834bf4c1775315c73a46 <52c3e242f4d0043186b70d65460ba1767f27494a
  3. Affected versionversion=773426f4771bdd82ac5c834bf4c1775315c73a46 <87bdfba903be7084cb3ee04032b14a81181fe413

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.16; version=773426f4771bdd82ac5c834bf4c1775315c73a46 <52c3e242f4d0043186b70d65460ba1767f27494a; version=773426f4771bdd82ac5c834bf4c1775315c73a46 <87bdfba903be7084cb3ee04032b14a81181fe413

Published CVSS scores

7.5LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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