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  4. CVE 2026 19953 uri versions before 536 for perl encode non nfc
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Back to active CVEs
Medium · CVSS 6.5CVE-2026-19953

URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprepCVE-2026-19953

Answer in brief

CVE-2026-19953 records a Medium severity (CVSS 6.5) vulnerability in URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep. The current sources do not mark it as known exploited. The current feed maps URI (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 31, 2026Updated Sep 3, 2026Source checked Oct 16, 2026First seen by HOL Aug 31, 2026Material review Sep 3, 2026
Upstream Advisory

Key facts

Risk
Medium · CVSS 6.5
Exploitation
Not marked as known exploited
Affected software
1 mapped package or product
Fix availability
Available

Why this deserves its current priority

CVSS is 6.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps URI (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
URIgeneric>=0 <5.365.36

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for URI.
  2. 2Review the reported fix. Source-reported solution: Upgrade to URI 5.36 or later.

Evidence timeline and material changes

  1. Published upstream

    Aug 31, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Sep 3, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Aug 31, 2026

Sources and claim methodology

  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • Source referencemetacpan.org
  • Source referencerfc-editor.org
  • Source referenceopenwall.com
Upstream source description

URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep. nameprep lowercases each host label but performs no Unicode normalization. IDNA requires a label to be normalized to Form C before it is encoded (RFC 5891), so a label that is not already in NFC is encoded to a different A-label than its normalized form. A label built from the precomposed Devanagari sequence U+0958 U+093E encodes to xn--72b5c without normalization but to xn--11b2fg after NFC normalization, and xn--72b5c does not round-trip back to the original label. Any caller that reads host() from a URI built from untrusted input and uses it for a security decision (an allow or deny list, an SSRF filter, deduplication, a cache key) sees the non-standard label, while a client that fetches the same URL resolves the NFC form, so the check and the fetch can disagree about the host.

Quoted source text, attributed separately from HOL analysis.

Related CVEs

  • ISPSoft Out-of-Bounds Read VulnerabilitySame generic ecosystem
  • ISPSoft Out-of-Bounds Read VulnerabilitySame generic ecosystem
  • CISA ADP VulnrichmentSame generic ecosystem
  • CISA ADP VulnrichmentSame generic ecosystem
  • CISA ADP VulnrichmentSame generic ecosystem
  • CISA ADP VulnrichmentSame generic ecosystem

Record context

Vulnerability class
SSRF
EPSS
Not reported
CWE IDs
CWE-1289
Source
CVE List V5
Source checked
Oct 16, 2026
References
5 linked sources
Open source record