CVE-2023-26131Public exploitNetwork attack vector

Browser script execution via unescaped missing-file path

Published May 31, 2023 · Updated Jan 9, 2025

Cross-site scripting in xyproto Algernon before 1.17.4 allows remote attackers to execute script in a user's browser through a missing-file URL. The NoPage function concatenates the requested filename into the not-found response body, and MessagePageBytes writes that body into HTML without escaping it. Exploitation requires a file or resource miss and user interaction with the crafted URL; script runs in the origin of the served Algernon site.

CVSS severity5.4
Medium
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in xyproto Algernon before 1.17.4 allows remote attackers to execute script in a user's browser through a missing-file URL. The NoPage function concatenates the requested filename into the not-found response body, and MessagePageBytes writes that body into HTML without escaping it. Exploitation requires a file or resource miss and user interaction with the crafted URL; script runs in the origin of the served Algernon site.

The record

CVE
CVE-2023-26131
Published
May 31, 2023
Updated
Jan 9, 2025
Vendor
xyproto
Product
Algernon
Classifications
CWE-79, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 31, 2023CVE publishedPublication date reported by the CVE source.
  2. Jan 9, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

xyproto · Algernonversion=0 <*

Published CVSS scores

6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
5.4SnykCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1204.001User Execution: Malicious Link

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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