CVE-2023-26131 — algernon
MEDIUMCVE-2023-26131 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in github.com/xyproto/algernon. 2 public exploit references exist, so weaponization risk is real. No vendor fix is recorded yet; mitigation options are listed below.
Algernon engine and themes vulnerable to Cross-site Scripting
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-26131.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2023-26131 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 383,485 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
github.com/xyproto/algernonReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
All versions of the package github.com/xyproto/algernon/engine; all versions of the package github.com/xyproto/algernon/themes are vulnerable to Cross-site Scripting (XSS) via the themes.NoPage(filename, theme) function due to improper user input sanitization. Exploiting this vulnerability is possible when a file/resource is not found.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/xyproto/algernon | all versions | No fix |
Affected Products
algernonalgernon_projectResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/xyproto/algernon, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of github.com/xyproto/algernon has shipped for CVE-2023-26131 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2023-26131 in your dependencies?
Find it across Go, including transitive dependencies.