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CVE-2026-63430Proof of concept (PoC) published · CISASuited to automated attack · CISA

ammonia: mXSS in ammonia via MathML `annotation-xml` encoding strip

CVSS score

6.3

EPSS probability

%0.6

Risk score

0.0

Published

3 d ago

OverviewPublic Exploits (0)NewsroomVulnerability Timeline
A patch is available only for some products or versions

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Impact on My Inventory

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Vulnerability description

CVE AI research

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DayBreach AI Explanation

Verified against sources

mXSS Vulnerability in ammonia Library

Sources read

2

Source agreement

Tam uyum

Evidence confidence

%63

Short explanation

The ammonia library contains a mutation cross-site scripting (mXSS) vulnerability when applications explicitly allow the math tag, annotation-xml, and at least one raw-text HTML element while disallowing the encoding attribute. This flaw can allow JavaScript execution due to namespace interpretation discrepancies between the sanitizer and the browser.

Why does it matter?

The vulnerability occurs when applications explicitly allow certain tags while stripping the encoding attribute. It can allow unauthenticated attackers to execute JavaScript when users render the sanitized output.

What should be done?

  • Upgrading the ammonia library to fixed releases
  • Following vendor advisories
  • Reviewing required tag configurations
Chain of evidence and sources2 verified claims

ammonia, güvenilmeyen HTML'yi onarmak ve güvenceye almak için kullanılan bir Rust kütüphanesidir.

S0 · daybreach-canonicalS1 · cvelistS2 · nvd

Gerekli etiketler varsayılan olarak etkinleştirilmemiştir, bu nedenle bunları açıkça izin vermeyen uygulamalar etkilenmez.

S0 · daybreach-canonicalS1 · cvelistS2 · nvd
Show the technical text from the sources

ammonia is a Rust library for repairing and securing untrusted HTML. Prior to 3.3.2, 4.0.2, and 4.1.3, applications that explicitly allow the math tag, annotation-xml, and at least one raw-text HTML element while disallowing the encoding attribute can permit mutation cross-site scripting. ammonia does not correctly implement annotation-xml's encoding-dependent MathML integration-point behavior after attribute filtering removes encoding, so the sanitizer validates a descendant under one namespace interpretation while the browser reparses the output under another. An attacker can use that namespace transition and an allowed raw-text HTML element to execute JavaScript when a user renders the sanitized output. The required tags are not enabled by default, so applications that do not explicitly allow them are not affected. This issue is fixed in versions 3.3.2, 4.0.2, and 4.1.3.

CVSS vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

CWE: CWE-79

Explanation produced with the local gemini-flash-lite-latest model. Numerical metrics and the KEV, patch and exploit statuses are not determined by AI.

IMPACT: Affected Products and Software

Affected Products

The following products are affected by CVE-2026-63430 vulnerability. Where our threat engine knows the exact affected versions, they are listed below.

IDVENDORPRODUCTACTION
1rust-ammoniaammonia View
2debianrust-ammonia (sid) View
3debianrust-ammonia (forky) View
4debianrust-ammonia (trixie) View
5debianrust-ammonia (bookworm) View
Total affected vendors: 2|Products: 5

RED HAT CSAF/VEX: Product Impact Check

Red Hat has not yet published a CSAF/VEX impact record for this CVE. This does not mean “not affected”.

SCORING: CVSS from Multiple Sources

CVSS Scores

The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.

SCOREVERSIONSEVERITYVECTORSOURCE
6.3CVSS V4_0MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:NCVE CNA
6.3CVSS V40MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XNVD

Patch and Remediation Guide

Solution & Remediation Advisory

Partial patch

2 düzeltme kanıtı bulundu; en az 2 ürün veya sürüm hâlâ etkileniyor ya da inceleniyor.

debianrust-ammonia (sid)4.1.3-1

Debian sid: 4.1.3-1

debianrust-ammonia (forky)4.1.3-1

Debian forky: 4.1.3-1

Confirm the affected product and version against the source evidence above.
Restrict access to internet-facing services and apply network segmentation.
Apply the official update named in the evidence only to the matching product and version.
Monitor server logs and network endpoints for signs of anomalous execution.

Public exploit and active exploitation status

Verified exploit intelligence

No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.

Weakness Classification and Attack Patterns (CWE & CAPEC)

CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-63430 is associated with the following CWEs:

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

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-63430 weaknesses.

CAPEC-66: SQL InjectionCAPEC-126: Path TraversalCAPEC-28: OS Command Injection

Attack Vector and Accessibility

ExposureAğ üzerinden
PermissionsGerekmiyor
UserGerekmiyor

Official Sources and Advisories

https://github.com/rust-ammonia/ammonia/security/advisories/GHSA-9jh8-v38h-cvhrvendor-advisoryhttps://github.com/rust-ammonia/ammonia/pull/243vendor-advisoryhttps://github.com/rust-ammonia/ammonia/pull/244vendor-advisoryhttps://github.com/rust-ammonia/ammonia/pull/245vendor-advisoryhttps://github.com/rust-ammonia/ammonia/commit/004bf2cee4288f74a6ee619d589e3e90c24c09cavendor-advisoryhttps://github.com/rust-ammonia/ammonia/commit/7ac3fd3145236f28857eeecbadb544c8659cba31vendor-advisoryhttps://github.com/rust-ammonia/ammonia/commit/b51bf4f9749ed3cd518330105f20a2c39c9ee274vendor-advisoryhttps://github.com/rust-ammonia/ammonia/releases/tag/v3.3.2vendor-advisoryhttps://github.com/rust-ammonia/ammonia/releases/tag/v4.0.2vendor-advisoryhttps://github.com/rust-ammonia/ammonia/releases/tag/v4.1.3vendor-advisory

CVSS Vector Radar Chart

6.3 / 10
Attack VectorNetworkComplexityLowPrivilegesNoneUser Interact.NoneConfidentialityLowIntegrityNoneAvailabilityNone

Vulnerability Scoring Details

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone required
User InteractionNone required
Confidentiality (Gizlilik)Low
Integrity (Bütünlük)None
Availability (Erişilebilirlik)None

Kısmi yama

2 düzeltme kanıtı bulundu; en az 2 ürün veya sürüm hâlâ etkileniyor ya da inceleniyor.

Follow the vendor

R
rust-ammonia logo
rust-ammonia
D
debian logo
debian

Weakness Type (CWE & CAPEC)

CWE-79

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