CVE-2026-13221

CRITICALNVD 9.1Trending — 4 sources updated this week
9.1
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 9.1Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Perl versions through 5.43.9 produce silently incorrect regular expression matches when an alternation of more than 65535 fixed string branches is compiled into a trie in Perl_study_chunk.

When such branches are combined into a trie, the delta between the first branch and the shared tail is stored in a 16-bit field. A branch count above 65535 overflows the field, and the trie's match decision table is truncated with no warning or error.

A pattern of this shape produces false positive matches (matching strings it should not) and false negative matches (failing to match strings it should). When such a pattern gates an access or filtering decision, the result is wrong.

CVSS v3
9.1
EG Score
0.0(none)
EPSS
45.0%
KEV
Not listed

Published

July 13, 2026

Last Modified

July 14, 2026

Advisory Details (2)

Auto-updated Jul 14, 2026
No patch confirmed yet.
generic

Regexp memory corruption with large tries · Issue #23388 · Perl/perl5 · GitHub

https://github.com/Perl/perl5/issues/23388
generic
https://github.com/Perl/perl5/commit/03f74bbbd3a68350d926ee93d56ee4808c28c4c7.patch

Vendor Advisories for CVE-2026-13221(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 8× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-15 16:57 UTCEPSS rescore
  2. 2026-07-15 02:00 UTCEPSS rescore
  3. 2026-07-14 13:45 UTCMITRE cvelistV5CVSS v3 → 9.1 · severity → CRITICAL
  4. 2026-07-13 20:25 UTCNVD update
  5. 2026-07-13 20:12 UTCMITRE cvelistV5
  6. 2026-07-13 18:08 UTCNVD update
  7. 2026-07-13 16:23 UTCEG score recompute
  8. 2026-07-13 16:22 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-13221?
CVE-2026-13221 is a critical vulnerability published on July 13, 2026. Perl versions through 5.43.9 produce silently incorrect regular expression matches when an alternation of more than 65535 fixed string branches is compiled into a trie in Perlstudychunk. When such branches are combined into a trie, the delta between the first branch and the shared tail is stored in…
When was CVE-2026-13221 disclosed?
CVE-2026-13221 was first published in the National Vulnerability Database on July 13, 2026, with the most recent update on July 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-13221 actively exploited?
CVE-2026-13221 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 45.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-13221?
CVE-2026-13221 has a CVSS v3 base score of 9.1 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 0.0.
How do I remediate CVE-2026-13221?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-13221, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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