CVE-2026-45721
📛 CVE Title
(no title)
Description
Algernon: handler.lua discovery walks parent directories above the server root
Description (MITRE) cveawg.mitre.org
Pulled from cveawg.mitre.org/api/cve/CVE-2026-45721 on 2026-07-12. Shown when MITRE's text differs from the cvelistV5 mirror.
Algernon is a small self-contained pure-Go web server. Prior to 1.17.7, when Algernon is asked for any URL path that resolves to a directory without an index file, DirPage walks upward through parent directories — past the configured server root — looking for a file named handler.lua to execute as the request handler. The loop terminates only after 100 ancestor steps or when filepath.Dir returns ., so on any absolute server-root path the search reaches the filesystem root (/ on Unix, drive letter on Windows). The first handler.lua it finds is loaded into the Lua interpreter with the full Algernon API exposed — including run3(), httpclient, os.execute, io.popen, PQ, MSSQL, raw filesystem access, and the userstate database. Any process that can write handler.lua anywhere in a parent directory of the server root obtains pre-authenticated remote code execution on the next HTTP request. This is reachable without authentication — the lookup happens before the permission check returns a hit (the perm system only gates URL prefixes, not the handler-resolution step), and any URL pointing at a directory without an index triggers the walk. On a fresh stock Algernon install the request GET / is enough. This vulnerability is fixed in 1.17.7.
Overview
- State
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- Assigner (CNA)
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- CVSS severity
- critical
- CVSS score
- 7.6 / 10
- CVSS vector
AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H- Effective score
- 7.6 / 10 CRITICAL source: CNA overview
- CWE(s)
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- Reserved
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- Published
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- Last updated
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- Source
- https://www.tenable.com/cve/CVE-2026-45721
- Linked Threat
- CVE-2026-45721 — CVE-2026-45721
NVD / KEV / EPSS data refreshed 2026-05-25 00:12 UTC. Re-run the 🛰 Backfill from NVD button above to refresh.
European Union Vulnerability Database ENISA EUVD
ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.
- EUVD ID
-
EUVD-2026-31867
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Vendor references (0)
References embedded in the original CVE record by the assigning CNA.
None in the CVE record.
Web references (4)
DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.
- https://github.com/xyproto/algernon/security/advisories/GHSA-xwcr-wm99-g9jc tenable:github.com
- https://www.first.org/epss/ tenable:www.first.org
- https://nvd.nist.gov/vuln/detail/CVE-2026-45721 tenable:nvd.nist.gov
- https://www.cve.org/CVERecord?id=CVE-2026-45721 tenable:www.cve.org
Remediations (10)
Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.
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web:blog.qualys.com
Oracle released its second quarterly edition of this year's Critical Patch Update. The update received patches for 481 security vulnerabilities.
2026-05-26 02:58 UTC -
web:blogs.oracle.com
For more information about the Critical Patch Update program, see the security vulnerability remediation practices page located on the Oracle Trust Center.
2026-05-26 02:58 UTC -
web:msrc.microsoft.com
The Microsoft Security Response Center (MSRC) investigates all reports of security vulnerabilities affecting Microsoft products and services, and provides the information here as part of the ongoing effort to help you manage security risks and help keep your systems protected.
2026-05-26 02:58 UTC -
web:support.servicenow.com
Overview The advisories below document publicly disclosed Common Vulnerabilities and Exposures ( CVEs ) in the Now Platform by ServiceNow. Because ServiceNow uses various methods to communicate vulnerability information, patches, and other fixes, customers should review family, security patch , and hotfix release notes, which are available at https://docs.servicenow.com, for a complete list of ...
2026-05-26 02:58 UTC -
web:www.crowdstrike.com
Microsoft's April 2026 Patch Tuesday addresses 164 CVEs , featuring 8 Critical vulnerabilities, one exploited zero-day, and one disclosed zero-day.
2026-05-26 02:58 UTC -
web:www.cve.org
At cve .org, we provide the authoritative reference method for publicly known information-security vulnerabilities and exposures
2026-05-26 02:58 UTC -
web:www.microsoft.com
These Knowledge Base articles accompany all security updates and advisories, and include caveats or known issues with security updates. Additionally, support engineers document common concerns from customers in these KB articles. These Knowledge Base articles are published the Security Update Guide with each release on Patch Tuesday.
2026-05-26 02:58 UTC -
web:www.oracle.com
This Critical Patch Update contains 481 new security patches across the product families listed below. Please note that an MOS note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at April 2026 Critical Patch Update: Executive Summary and Analysis.
2026-05-26 02:58 UTC -
web:www.oracle.com
Oracle Critical Patch Update Advisory - January 2026 Description A Critical Patch Update is a collection of patches for multiple security vulnerabilities. These patches address vulnerabilities in Oracle code and in third party components included in Oracle products. These patches are usually cumulative, but each advisory describes only the security patches added since the previous Critical ...
2026-05-26 02:58 UTC -
web:www.securityweek.com
Oracle on Tuesday announced the release of 481 new security patches as part of its April 2026 Critical Patch Update (CPU). Across the 28 product families that received security updates, more than 300 patches address vulnerabilities that are remotely exploitable without authentication.
2026-05-26 02:58 UTC
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