SWC HTML minifier may allow script element breakout when minifying embedded JSON

published 2026-08-11 2 mo ago modified 2026-09-18 51 d ago also GHSA-5qr2-v392-m9g8 , EUVD-2026-56179

cvss: 6.1; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 27%
public exploits: 0; none known

SWC is a TypeScript / JavaScript compiler written in Rust. Prior to @swc/html 1.15.47-nightly-20260729.1 and swc_html_minifier 59.0.0, the minifyJson processing in crates/swc_html_minifier/src/lib.rs parsed and serialized attacker-controlled JSON in application/json and application/ld+json script elements without the escape_json_for_html_script behavior to re-escape less-than signs, allowing a closing script sequence to terminate the element early and execute script in the generated page's origin. This issue is fixed in @swc/html 1.15.47-nightly-20260729.1 and swc_html_minifier 59.0.0.

Patch / fix

fixed in 2 links 4

npm @swc/html 1.15.47-nightly-20260729.1
crates.io swc_html_minifier 59.0.0

github.com/swc-project/swc@e1877b4 commit
github.com/swc-project/swc#12080 pull request
github.com/swc-project/swc/releases/tag/v1.15.47 release
github.com/swc-project/swc/releases/tag/v1.15.47-nightly-20260729.1 release

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 2 mo ago (2026-08-11)

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	6.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
GitHub	3.1	6.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	@swc/html	<1.15.47-nightly-20260729.1	1.15.47-nightly-20260729.1
crates.io	swc_html_minifier	<59.0.0	59.0.0

Affected products

swc-project swc
@swc html
swc-project swc_html_minifier

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation
CWE-116 Improper Encoding or Escaping of Output

References

Sources

Fencer Vulns 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.

Summary