CWE-86Improper Neutralization of Invalid Characters in Identifiers in Web Pages

Abstraction: Variant · CVEs in our corpus: 11

The product does not neutralize or incorrectly neutralizes invalid characters or byte sequences in the middle of tag names, URI schemes, and other identifiers.

Some web browsers may remove these sequences, resulting in output that may have unintended control implications. For example, the product may attempt to remove a "javascript:" URI scheme, but a "java%00script:" URI may bypass this check and still be rendered as active javascript by some browsers, allowing XSS or other attacks.

Last updated: 15 October 2026 14:21 UTC

OWASP Top 10 for Web (2025)

This weakness contributes to A05:2025 Injection.

Control responseHuman-reviewed

Answering this weakness across the control lifecycle, from our framework cross-walks.

Prevent

Stop it (NIST 800-53 / CSF Protect)

PR.PS-06
SI-10 Information Input Validation

Detect

Catch it (CSF Detect / Respond)

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Harden

Shrink the surface (DISA STIG)

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Validate

Prove the fix (OWASP ASVS)

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NIST 800-53 r5 controls PROPOSED for this weakness (0)AI-assisted

These are model PROPOSALS, not graded mappings. They come from controls_to_cwe_proposals, which carries no grade field at all; across the CWE pages 1,540 of 1,722 such associations (89%) have never been graded by anything. The heading said “address” until 2026-09-29, which asserted a relationship the data does not carry. Graded cross-walks are on the framework map, not here.

Control	Title	Family	Why it addresses this CWE
No NIST controls proposed yet.

Top CVEs of this weakness type, ranked by Risk Priority

CVE	Risk	CVSS	EPSS	Published
`CVE-2025-66606`	6.6	9.6	0.0026	2026-02-09
`CVE-2023-31126`	6.5	9.0	0.0082	2023-05-09
`CVE-2024-21864`	5.5	7.8	0.0034	2024-05-16
`CVE-2024-10941`	5.1	6.5	0.0043	2024-11-06
`CVE-2021-33158`	5.0	7.2	0.0021	2024-02-23
`CVE-2026-71478`	4.6	6.1	0.0036	2026-08-06
`CVE-2025-20166`	4.2	5.4	0.0036	2025-01-08
`CVE-2025-20167`	4.1	5.4	0.0028	2025-01-08
`CVE-2025-20168`	4.1	5.4	0.0028	2025-01-08
`CVE-2026-28417`	4.0	4.4	0.0143	2026-02-27
`CVE-2023-22840`	3.0	3.3	0.0043	2023-08-11