CVE-2026-63430Public exploitNetwork attack vector

JavaScript execution via annotation-xml encoding removal

Published Oct 15, 2026 · Updated Oct 15, 2026

Mutation XSS in rust-ammonia Ammonia allows remote attackers to execute JavaScript via crafted HTML in non-default configurations. The check_expected_namespace function treats annotation-xml as an unconditional HTML integration point, accepting descendants whose interpretation changes after encoding removal. Exploitation requires explicitly allowed math, annotation-xml, and a raw-text HTML element, disallowed encoding, and browser rendering of sanitized output; execution occurs in the application's origin.

CVSS severity6.3
Medium
EPSS probability0.55%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Mutation XSS in rust-ammonia Ammonia allows remote attackers to execute JavaScript via crafted HTML in non-default configurations. The check_expected_namespace function treats annotation-xml as an unconditional HTML integration point, accepting descendants whose interpretation changes after encoding removal. Exploitation requires explicitly allowed math, annotation-xml, and a raw-text HTML element, disallowed encoding, and browser rendering of sanitized output; execution occurs in the application's origin.

The record

CVE
CVE-2026-63430
Published
Oct 15, 2026
Updated
Oct 15, 2026
Vendor
rust-ammonia
Product
Ammonia
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=< 3.3.2
  2. Affected versionversion=>= 4.0.0, < 4.0.2
  3. Affected versionversion=>= 4.1.0, < 4.1.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

rust-ammonia · Ammoniaversion=< 3.3.2; version=>= 4.0.0, < 4.0.2; version=>= 4.1.0, < 4.1.3

Published CVSS scores

6.3rust-ammoniaCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA: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.

Activity data is delayed. The latest report is Sep 28, 2026.

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

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 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')
T1059.007JavaScript

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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