# CVE-2026-9499: Out-of-bounds read in QTextCodec::codecForName() in Qt > An out-of-bounds read in Qt's QTextCodec can cause a denial of service when processing non-NUL-terminated byte arrays. - **Severity:** Medium 6.3 (`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`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 21 Jul 2026 - **Updated:** 22 Jul 2026 - **Also known as:** ALSA-2026:65816, ALSA-2026:65897, ALSA-2026:65993, CLSA-2026-1789398784, DEBIAN-CVE-2026-9499, ECHO-5c6a-872b-49bb, GHSA-8cm2-5hwv-mhv9, OESA-2026-3202, OESA-2026-3203, OESA-2026-3936, OESA-2026-3937, OESA-2026-3938, OESA-2026-3939, OESA-2026-4062, OESA-2026-4099, RHSA-2026:41389, RHSA-2026:65816, RHSA-2026:65897, RHSA-2026:65993, RHSA-2026:70560, RHSA-2026:70561, RHSA-2026:70562, RHSA-2026:72376, RHSA-2026:72377, RHSA-2026:72378, RHSA-2026:72383, RHSA-2026:74444, RLSA-2026:65816, RLSA-2026:65897, RLSA-2026:65993, UBUNTU-CVE-2026-9499 ## What is CVE-2026-9499? CVE-2026-9499 is a medium-severity memory corruption vulnerability in Qt, published on 21 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official 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. Weakness: CWE-125 (Out-of-bounds Read) ## Which versions are affected by CVE-2026-9499? | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `qt6-qt5compat` | AlmaLinux:10 | All versions | 6.10.1-1.el10_2.1 | | `qt6-qt5compat-devel` | AlmaLinux:10 | All versions | 6.10.1-1.el10_2.1 | | `qt6-qt5compat-examples` | AlmaLinux:10 | All versions | 6.10.1-1.el10_2.1 | | `qt5-qtbase` | AlmaLinux:8 | All versions | 5.15.3-9.el8_10 | | `qt5-qtbase-common` | AlmaLinux:8 | All versions | 5.15.3-9.el8_10 | | `qt5-qtbase-devel` | AlmaLinux:8 | All versions | 5.15.3-9.el8_10 | | `qt5-qtbase-examples` | AlmaLinux:8 | All versions | 5.15.3-9.el8_10 | | `qt5-qtbase-gui` | AlmaLinux:8 | All versions | 5.15.3-9.el8_10 | | `qt5-qtbase-mysql` | AlmaLinux:8 | All versions | 5.15.3-9.el8_10 | | `qt5-qtbase-odbc` | AlmaLinux:8 | All versions | 5.15.3-9.el8_10 | | `qt5-qtbase-postgresql` | AlmaLinux:8 | All versions | 5.15.3-9.el8_10 | | `qt5-qtbase-private-devel` | AlmaLinux:8 | All versions | 5.15.3-9.el8_10 | | `qt5-qtbase-static` | AlmaLinux:8 | All versions | 5.15.3-9.el8_10 | | `qt5-qtbase` | AlmaLinux:9 | All versions | 5.15.9-11.el9_8.1 | | `qt5-qtbase-common` | AlmaLinux:9 | All versions | 5.15.9-11.el9_8.1 | | `qt5-qtbase-devel` | AlmaLinux:9 | All versions | 5.15.9-11.el9_8.1 | | `qt5-qtbase-examples` | AlmaLinux:9 | All versions | 5.15.9-11.el9_8.1 | | `qt5-qtbase-gui` | AlmaLinux:9 | All versions | 5.15.9-11.el9_8.1 | | `qt5-qtbase-mysql` | AlmaLinux:9 | All versions | 5.15.9-11.el9_8.1 | | `qt5-qtbase-odbc` | AlmaLinux:9 | All versions | 5.15.9-11.el9_8.1 | | `qt5-qtbase-postgresql` | AlmaLinux:9 | All versions | 5.15.9-11.el9_8.1 | | `qt5-qtbase-private-devel` | AlmaLinux:9 | All versions | 5.15.9-11.el9_8.1 | | `qt5-qtbase-static` | AlmaLinux:9 | All versions | 5.15.9-11.el9_8.1 | | `qt6-qt5compat` | Red Hat:enterprise_linux:10.2 | All versions | 0:6.10.1-1.el10_2.1 | | `qt6-qt5compat-debuginfo` | Red Hat:enterprise_linux:10.2 | All versions | 0:6.10.1-1.el10_2.1 | | `qt6-qt5compat-debugsource` | Red Hat:enterprise_linux:10.2 | All versions | 0:6.10.1-1.el10_2.1 | | `qt6-qt5compat-devel` | Red Hat:enterprise_linux:10.2 | All versions | 0:6.10.1-1.el10_2.1 | | `qt6-qt5compat-examples` | Red Hat:enterprise_linux:10.2 | All versions | 0:6.10.1-1.el10_2.1 | | `qt6-qt5compat-examples-debuginfo` | Red Hat:enterprise_linux:10.2 | All versions | 0:6.10.1-1.el10_2.1 | | `qt6-qt5compat-tests-debuginfo` | Red Hat:enterprise_linux:10.2 | All versions | 0:6.10.1-1.el10_2.1 | | `qt5-qtbase` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.15.3-9.el8_10 | | `qt5-qtbase-common` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.15.3-9.el8_10 | | `qt5-qtbase-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.15.3-9.el8_10 | | `qt5-qtbase-debugsource` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.15.3-9.el8_10 | | `qt5-qtbase-devel` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.15.3-9.el8_10 | | `qt5-qtbase-devel-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.15.3-9.el8_10 | | `qt5-qtbase-examples` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.15.3-9.el8_10 | | `qt5-qtbase-examples-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.15.3-9.el8_10 | | `qt5-qtbase-gui` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.15.3-9.el8_10 | | `qt5-qtbase-gui-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.15.3-9.el8_10 | ## How do I fix CVE-2026-9499? Apply the vendor's patch. ## Is CVE-2026-9499 being exploited? There is no known exploitation of CVE-2026-9499 in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-9499 and fix it if it is affected. What it is: CVE-2026-9499 is a medium-severity memory corruption vulnerability in Qt, published on 21 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-9499 in the wild and no public exploit code. Affected product: Qt. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-9499/ (Markdown: https://insights.sbomify.com/CVE-2026-9499/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-9499 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-9499 - OSV: https://osv.dev/vulnerability/CVE-2026-9499 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-9499/ Summaries are generated and may contain mistakes; the official description above is the record.