CVE-2026-31391

RNG read denial via leaked operation counter

Published Apr 3, 2026 · Updated Apr 3, 2026

Denial of service in the Linux kernel's atmel-sha204a driver allows local users to block future random-number reads after memory exhaustion. In atmel_sha204a_rng_read_nonblocking, the driver increments tfm_count before allocating work data but returns on kmalloc failure without decrementing it. The stale count stays at the one-request limit, so later nonblocking reads return no data; reachability requires the SHA204A hardware RNG and a local allocation failure.

CVSS severity5.5
Medium
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in the Linux kernel's atmel-sha204a driver allows local users to block future random-number reads after memory exhaustion. In atmel_sha204a_rng_read_nonblocking, the driver increments tfm_count before allocating work data but returns on kmalloc failure without decrementing it. The stale count stays at the one-request limit, so later nonblocking reads return no data; reachability requires the SHA204A hardware RNG and a local allocation failure.

The record

CVE
CVE-2026-31391
Published
Apr 3, 2026
Updated
Apr 3, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 3, 2026Record 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=5.3
  2. Affected versionversion=da001fb651b00e1deeaf24767dd691ae8152a4f5 <1ab70c260cf16f931a728b2cb63fff5f38c814d8
  3. Affected versionversion=da001fb651b00e1deeaf24767dd691ae8152a4f5 <2bfc83cee05f8b9604502df27d94e8e2b4a3dbf1
  4. Affected versionversion=da001fb651b00e1deeaf24767dd691ae8152a4f5 <66ee9c1c3575b5d6afc340faca00fd40ed5b7ad9
  5. Affected versionversion=da001fb651b00e1deeaf24767dd691ae8152a4f5 <6f502049a96b368ea6646c49d9520d6f69a101fa
  6. Affected versionversion=da001fb651b00e1deeaf24767dd691ae8152a4f5 <d240b079a37e90af03fd7dfec94930eb6c83936e
  7. Affected versionversion=da001fb651b00e1deeaf24767dd691ae8152a4f5 <fd262dc6d758232511127372eba866b7600739ba

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=5.3; version=da001fb651b00e1deeaf24767dd691ae8152a4f5 <1ab70c260cf16f931a728b2cb63fff5f38c814d8; version=da001fb651b00e1deeaf24767dd691ae8152a4f5 <2bfc83cee05f8b9604502df27d94e8e2b4a3dbf1; version=da001fb651b00e1deeaf24767dd691ae8152a4f5 <66ee9c1c3575b5d6afc340faca00fd40ed5b7ad9; version=da001fb651b00e1deeaf24767dd691ae8152a4f5 <6f502049a96b368ea6646c49d9520d6f69a101fa; version=da001fb651b00e1deeaf24767dd691ae8152a4f5 <d240b079a37e90af03fd7dfec94930eb6c83936e; version=da001fb651b00e1deeaf24767dd691ae8152a4f5 <fd262dc6d758232511127372eba866b7600739ba

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/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)
Vectorlocal
Privilegesauthenticated
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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