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CVE-2026-9499— Out-of-bounds read in QTextCodec::codecForName() in Qt

Quick assessment

Affected
Qt Qt
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Qt是Qt公司开源的一个跨平台的应用程序开发框架。 Qt 6.0.0之前版本、6.0.0至6.8.8之前版本、6.9.0至6.11.1之前版本以及4.x和5.x版本存在缓冲区错误漏洞，该漏洞源于QTextCodec::codecForName()函数存在缓冲区过读取，当使用非NUL终止的QByteArray调用该函数时，编码名称匹配例程会读取超出提供的缓冲区末尾，在最坏情况下若过读取到达未映射内存，则导致进程崩溃。

AI Predicted 5.5 Difficulty: Moderate EPSS 0.30% · P23

Possible ATT&CK Techniques 1 AI

T1211 · Exploitation for Stealth

Affected Version Matrix 3

VendorProduct Version RangeStatus
Qt Qt 6.0.0< 6.8.8 affected
6.9.0< 6.11.1 affected
4.0.0< 6.0.0 affected
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I. Basic Information for CVE-2026-9499

Vulnerability Information
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Vulnerability Title
Out-of-bounds read in QTextCodec::codecForName() in Qt
Source: CVE Program / CVE List V5
Vulnerability Description
An out-of-bounds read (buffer over-read) vulnerability exists in QTextCodec::codecForName() in Qt. When the function is called with a QByteArray that is not NUL-terminated (for example, one created with QByteArray::fromRawData()), the codec-name matching routine reads past the end of the supplied buffer. In most cases this results in an incorrect text codec being selected; in the worst case, if the over-read reaches unmapped memory, the process crashes (denial of service). The over-read is bounded by the length of the longest codec-name candidate, and the out-of-bounds bytes are only compared internally against Qt's fixed list of codec names, so no data is disclosed to an attacker. Applications that do not pass non-NUL-terminated QByteArrays to QTextCodec::codecForName() are not exposed. The affected code resides in the Qt5Compat module from Qt 6.0.0 onward, and in Qt Core (qtbase) in Qt 4.x and Qt 5.x.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存读
Source: CVE Program / CVE List V5
Vulnerability Title
Qt 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Qt是Qt公司开源的一个跨平台的应用程序开发框架。 Qt 6.0.0之前版本、6.0.0至6.8.8之前版本、6.9.0至6.11.1之前版本以及4.x和5.x版本存在缓冲区错误漏洞，该漏洞源于QTextCodec::codecForName()函数存在缓冲区过读取，当使用非NUL终止的QByteArray调用该函数时，编码名称匹配例程会读取超出提供的缓冲区末尾，在最坏情况下若过读取到达未映射内存，则导致进程崩溃。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Qt Qt 6.0.0 ~ 6.8.8 cpe:2.3:a:qt:qt:*:*:*:*:*:*:*:*
Qt Qt 4.0.0 ~ 6.0.0 cpe:2.3:a:qt:qt:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-9499

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III. Intelligence Information for CVE-2026-9499

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Patches & Fixes for CVE-2026-9499 (4)

IV. Related Vulnerabilities

Same product: Qt
Same vendor: Qt
Same weakness: CWE-125

V. Comments for CVE-2026-9499

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