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MEDIUM severity

CVE-2023-26131 — algernon

MEDIUM

CVE-2023-26131 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in github.com/xyproto/algernon. 2 public exploit or proof-of-concept references are indexed, so weaponization risk is real. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

Algernon engine and themes vulnerable to Cross-site Scripting

Published
Updated
Affected
1 pkg
Patched
See advisory
Exploits
2 known
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs53th percentile — riskier than 53% of all scored CVEsHighest risk
0.00%0.40%0.79%1.19%0.3%0.7%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐹github.com/xyproto/algernon

Real-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

1 total
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/xyproto/algernonall versionsNo fix

Affected Products

1 product · 1 configurations
Application
algernonalgernon_project
all
Exploits & PoCs
2

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

All versions of the package github.com/xyproto/algernon/engine; all vers…

security.snyk.ioNVDJun 2023

Report on security.snyk.io

security.snyk.ioNVDJun 2023

Detection & mitigation playbook

Open-source dependency

  1. Detect

    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.

  2. Remediation status

    The records we use list no patched version of github.com/xyproto/algernon for CVE-2023-26131. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

  3. 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

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.
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CVE-2023-26131: algernon XSS (Medium 6.1)