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Fencer Intel
medium 6.3

CVE-2026-63430 json

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

published 4mo ago modified 20d ago also EUVD-2026-102241 , GHSA-9jh8-v38h-cvhr , RUSTSEC-2026-0193

cvss
6.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 46%
public exploits
0
none known

Summary

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.

Patch / fix

  • crates.io ammonia 3.3.2, 4.0.2, 4.1.3
  • ammonia_project ammonia 3.3.2, 4.0.2, 4.1.3
  • rust-ammonia Debian 14 4.1.3-1

debian advisories DEBIAN-CVE-2026-63430

  • gnome-podcasts openSUSE Leap 16.0 0.7.1-bp160.1.1

opensuse advisories openSUSE-SU-2026:22255-1

Is CVE-2026-63430 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-63430 updated cvss 4.7

ammonia: ammonia: Cross-site scripting via improper MathML namespace handling

  • Red Hat Ansible Automation Orchestrator 2026 ansible-automation-platform/automation-orchestrator-backend-rhel9
    affected: no fix available “Fix deferred”
  • Red Hat Ansible Automation Platform 2 python3.12-nh3 0.3.6-1.el9ap, python3.11-nh3 0.2.18-1.el9ap, ansible-automation-platform-26/hub-rhel9, ansible-automation-platform-27/hub-rhel9, ansible-automation-platform-26/gateway-rhel9, ansible-automation-platform-27/gateway-rhel9, +7 more
    affected: no fix available, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 rls, rust, cargo, clippy, rustfmt, rust-gdb, +8 more Red Hat Enterprise Linux 9 rust, cargo, clippy, rustfmt, rust-gdb, rust-src, +9 more Red Hat Enterprise Linux 10 rust 1.84.1-1.el10_0.4 Red Hat Satellite 6 python3.12-nh3 0.3.6-1.el9ap
    affected: no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
27d ago

Exploit prediction

0.56% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/rust-ammonia/ammonia/security/advisories/GHSA-9jh8-v38h-cvhr referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 6.3 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
CNA 4.0 6.3 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/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:X

Affected packages

ecosystem package affected fixed in
crates.io ammonia
<3.3.2
>=4.0.0, <4.0.2
>=4.1.0, <4.1.3
>=0.0.0-0, <3.3.2
3.3.2
4.0.2
4.1.3

Affected products

  • rust-ammonia ammonia

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.