CVE-2026-74655

UART hang via DMA flush race

Published Aug 22, 2026 · Updated Aug 25, 2026

Denial of service in the Linux kernel qcom-geni UART driver allows local users to hang tcdrain calls through a transmit flush. DMA-mode uart_ops lacks flush_buffer, allowing an in-flight transfer to complete after the serial core resets the transmit kfifo, underflow its length, and resubmit page-sized transfers indefinitely. A large userspace write followed immediately by TCOFLUSH on an affected Qualcomm GENI UART triggers repeated corrupted DMA frames; a later tcdrain hangs forever.

CVSS severity8.8
High
EPSS probability0.13%
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 qcom-geni UART driver allows local users to hang tcdrain calls through a transmit flush. DMA-mode uart_ops lacks flush_buffer, allowing an in-flight transfer to complete after the serial core resets the transmit kfifo, underflow its length, and resubmit page-sized transfers indefinitely. A large userspace write followed immediately by TCOFLUSH on an affected Qualcomm GENI UART triggers repeated corrupted DMA frames; a later tcdrain hangs forever.

The record

CVE
CVE-2026-74655
Published
Aug 22, 2026
Updated
Aug 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-835, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 25, 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=2aaa43c7077833301c237684cd7bc9ae5e3dec95 <1c31e2377f4c1bb110ca7f6e597b2253a7440c37
  2. Affected versionversion=2aaa43c7077833301c237684cd7bc9ae5e3dec95 <313ae287442e5e8d3f7b53b73f37d384bda072d0
  3. Affected versionversion=2aaa43c7077833301c237684cd7bc9ae5e3dec95 <b1801c0d40f62778b613334de5840aba10a564d5
  4. Affected versionversion=2aaa43c7077833301c237684cd7bc9ae5e3dec95 <e3c04834ae1ab5e9cfbe8ac54ec734aa4774249d
  5. Affected versionversion=6.3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2aaa43c7077833301c237684cd7bc9ae5e3dec95 <1c31e2377f4c1bb110ca7f6e597b2253a7440c37; version=2aaa43c7077833301c237684cd7bc9ae5e3dec95 <313ae287442e5e8d3f7b53b73f37d384bda072d0; version=2aaa43c7077833301c237684cd7bc9ae5e3dec95 <b1801c0d40f62778b613334de5840aba10a564d5; version=2aaa43c7077833301c237684cd7bc9ae5e3dec95 <e3c04834ae1ab5e9cfbe8ac54ec734aa4774249d; version=6.3

Published CVSS scores

8.8Linux kernel CVE teamCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
5.5Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5Red HatCVSS: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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