CVE-2021-25987

Stored XSS via unescaped tag names

Published Nov 30, 2021 · Updated Apr 30, 2025

Stored XSS in Hexo 0.0.1 through 5.4.0 allows local users to execute script in site visitors' browsers through crafted tags. The listTags helper appends tag.name directly to anchor text when no transform is configured, rather than applying HTML entity escaping. Exploitation requires prior ability to modify site source and a visitor to load the generated page, where the script runs in the site's browser origin.

CVSS severity4.6
Medium
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Hexo 0.0.1 through 5.4.0 allows local users to execute script in site visitors' browsers through crafted tags. The listTags helper appends tag.name directly to anchor text when no transform is configured, rather than applying HTML entity escaping. Exploitation requires prior ability to modify site source and a visitor to load the generated page, where the script runs in the site's browser origin.

The record

CVE
CVE-2021-25987
Published
Nov 30, 2021
Updated
Apr 30, 2025
Vendor
Hexo
Product
Hexo
Classifications
CWE-79, T1189
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Nov 30, 2021CVE publishedPublication date reported by the CVE source.
  2. Apr 30, 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=next of 0.0.1 <unspecified
  2. Affected versionversion=unspecified <=5.4.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

Hexo · Hexoversion=next of 0.0.1 <unspecified; version=unspecified <=5.4.0

Published CVSS scores

4.6NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
1.9NIST NVDAV:L/AC:M/Au:N/C:N/I:P/A:N
5.0MendCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

Public exploit references

No public exploit references are available in this record.

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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