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Vulnerabilities

Vulnerability · RUSTSEC-2026-0373

Missing case-insensitive matching for CSS url function

Published Oct 16, 2026 · catalog updated Oct 17, 2026 · Missing case-insensitive matching for

Open the advisory

Exploitation likelihood is not on this record for RUSTSEC-2026-0373. A missing EPSS score is not a low risk. Compare Missing case-insensitive matching for with the linked advisory before you change production.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Missing case-insensitive matching for).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
  • EPSS is missing. A missing score is not a low risk.
Severity
Unknown—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
Awaiting synchronization with FIRST
Remediation
Advisory link
Affected products
crates.io ammonia

URL filtering, such as relative URLs and URL scheme limits, is not always applied when CSS sanitization is used. When the inner URL is quoted, CSS is matched case-sensitively, when it should be matched case-insensitively. As a result, while gets the intended domain name filtering, does not. The following example shows how an application needs to be configured to trigger this bug. This can be used to inject tracking pixels where the application intended to prevent them. It does not allow XSS, and its usefulness for data exfiltration is limited. --- This vulnerability was reported by [Louis Li](https://github.com/zhixuli0406).

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • crates.io ammonia0.0.0-0 → 4.1.8

How to fix RUSTSEC-2026-0373

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

Exploitation likelihood is not on this record for RUSTSEC-2026-0373. A missing EPSS score is not a low risk. Compare Missing case-insensitive matching for with the linked advisory before you change production.

Which versions are affected?

Compare what you have installed with 0.0.0-0 → 4.1.8. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS is not on this record yet. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 16, 2026 · GitHub Advisory Database

    Detected

    URL filtering, such as relative URLs and URL scheme limits, is not always applied when CSS sanitization is used. When the inner URL is quoted, CSS is matched case-sensitively, when it should be matched case-insensitively. As a result, while gets the intended domain name filtering, does not. The following example shows how an application needs to be configured to trigger this bug. This can be used

  2. Oct 17, 2026 · GitHub Advisory Database

    Fix available

    ammonia fixed in 4.1.8

  3. Oct 17, 2026 · GitHub Advisory Database

    Fix available

    ammonia fixed in 4.1.8

  4. Oct 17, 2026 · GitHub Advisory Database

    Updated

    URL filtering, such as relative URLs and URL scheme limits, is not always applied when CSS sanitization is used. When the inner URL is quoted, CSS is matched case-sensitively, when it should be matched case-insensitively. As a result, while gets the intended domain name filtering, does not. The following example shows how an application needs to be configured to trigger this bug. This can be used

Sources

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.