CVE-2026-13221

CRITICALNVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-07-13. NVD baseline CVSS 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — Patch released this week
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.1Exploit: None knownExposed: 0

A fix is available — apply it.

Perl versions before 5.40.5-RC1, from 5.41.0 before 5.42.3-RC1, from 5.43.0 before 5.43.10 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
9.1(medium)
EG Risk
56(Track)
EG Risk 56/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity91% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
37%
KEV
Not listed

Published

July 13, 2026

Last Modified

September 8, 2026

Advisory Details (3)

Auto-updated Sep 15, 2026
No patch confirmed yet.
generic

oss-security - CVE-2026-13221: 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

http://www.openwall.com/lists/oss-security/2026/07/13/5
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(3)

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

Patch Availability(8)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuperl-modules-5.40 (5.40.1-7ubuntu0.3) @ resolute2026-09-18ubuntu
ubuntuperl-modules-5.26 (5.26.1-6ubuntu0.7+esm3) @ bionic2026-09-18ubuntu
ubuntuperl-modules-5.38 (5.38.2-3.2ubuntu0.4) @ noble2026-09-18ubuntu
redhatperl-4:5.40.2-515.el10_22026-09-14redhat
redhatperl-4:5.26.3-423.el8_10.12026-09-14redhat
redhatperl:5.32-8100020260826134600.651ee29f2026-09-14redhat
redhatperl-4:5.32.1-484.el9_82026-09-14redhat
redhatperl-main-1.03-524.3.hum12026-07-15redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
perl5.32.1-4 ... 5.44.0-1 (59 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
perl5.36.0-10 ... 5.44.0-1 (43 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
perl5.40.1-6 ... 5.44.0-1 (11 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
perl5.40.1-6 ... 5.42.2-3 (9 versions)5.42.3-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(7)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 17× in last 7d / 151× 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.

Showing the most recent 100 of 535 total refreshes for this CVE.

  1. 2026-09-20 20:15 UTCEPSS rescore
  2. 2026-09-18 19:27 UTCEPSS rescore
  3. 2026-09-18 10:06 UTCVendor advisory
  4. 2026-09-18 10:06 UTCGHSA enrichment
  5. 2026-09-18 05:02 UTCEG score recompute
  6. 2026-09-18 05:02 UTCVendor advisory
  7. 2026-09-18 05:02 UTCGHSA enrichment
  8. 2026-09-16 05:14 UTCEPSS rescore
  9. 2026-09-14 11:07 UTCVendor advisory
  10. 2026-09-14 11:07 UTCGHSA enrichment
  11. 2026-09-14 06:51 UTCVendor advisory
  12. 2026-09-14 06:51 UTCGHSA enrichment
  13. 2026-09-14 03:11 UTCVendor advisory
  14. 2026-09-14 03:11 UTCGHSA enrichment
  15. 2026-09-13 23:32 UTCEG score recompute
  16. 2026-09-13 23:32 UTCVendor advisory
  17. 2026-09-13 23:32 UTCGHSA enrichment
  18. 2026-09-13 16:46 UTCEPSS rescore
  19. 2026-09-13 16:30 UTCVendor advisory
  20. 2026-09-13 16:30 UTCGHSA enrichment
  21. 2026-09-13 11:51 UTCVendor advisory
  22. 2026-09-13 11:51 UTCGHSA enrichment
  23. 2026-09-13 08:00 UTCVendor advisory
  24. 2026-09-13 08:00 UTCGHSA enrichment
  25. 2026-09-12 17:09 UTCEG score recompute
Show 75 more
  1. 2026-09-12 17:09 UTCVendor advisory
  2. 2026-09-12 17:09 UTCGHSA enrichment
  3. 2026-09-12 15:00 UTCEPSS rescore
  4. 2026-09-12 13:27 UTCVendor advisory
  5. 2026-09-12 13:27 UTCGHSA enrichment
  6. 2026-09-12 07:32 UTCVendor advisory
  7. 2026-09-12 07:32 UTCGHSA enrichment
  8. 2026-09-12 01:51 UTCEG score recompute
  9. 2026-09-12 01:51 UTCVendor advisory
  10. 2026-09-12 01:51 UTCGHSA enrichment
  11. 2026-09-11 14:52 UTCEPSS rescore
  12. 2026-09-11 09:36 UTCEPSS rescore
  13. 2026-09-10 09:34 UTCEPSS rescore
  14. 2026-09-08 22:52 UTCEG score recompute
  15. 2026-09-08 22:52 UTCVendor advisory
  16. 2026-09-08 22:52 UTCGHSA enrichment
  17. 2026-09-08 22:00 UTCEPSS rescore
  18. 2026-09-08 01:57 UTCEG score recompute
  19. 2026-09-08 01:57 UTCVendor advisory
  20. 2026-09-08 01:57 UTCGHSA enrichment
  21. 2026-09-07 16:01 UTCEPSS rescore
  22. 2026-09-06 13:50 UTCEG score recompute
  23. 2026-09-06 13:50 UTCVendor advisory
  24. 2026-09-06 13:50 UTCGHSA enrichment
  25. 2026-09-06 13:47 UTCEPSS rescore
  26. 2026-09-06 05:23 UTCVendor advisory
  27. 2026-09-06 05:23 UTCGHSA enrichment
  28. 2026-09-06 01:36 UTCVendor advisory
  29. 2026-09-06 01:36 UTCGHSA enrichment
  30. 2026-09-05 21:25 UTCEG score recompute
  31. 2026-09-05 21:25 UTCVendor advisory
  32. 2026-09-05 21:25 UTCGHSA enrichment
  33. 2026-09-04 05:06 UTCEPSS rescore
  34. 2026-09-02 14:11 UTCEPSS rescore
  35. 2026-09-01 13:53 UTCEPSS rescore
  36. 2026-09-01 04:39 UTCEPSS rescore
  37. 2026-08-30 23:45 UTCVendor advisory
  38. 2026-08-30 23:45 UTCGHSA enrichment
  39. 2026-08-30 20:06 UTCEG score recompute
  40. 2026-08-30 20:06 UTCVendor advisory
  41. 2026-08-30 20:06 UTCGHSA enrichment
  42. 2026-08-30 19:17 UTCEPSS rescore
  43. 2026-08-30 16:26 UTCVendor advisory
  44. 2026-08-30 16:26 UTCGHSA enrichment
  45. 2026-08-30 10:59 UTCVendor advisory
  46. 2026-08-30 10:59 UTCGHSA enrichment
  47. 2026-08-30 05:29 UTCEG score recompute
  48. 2026-08-30 05:29 UTCVendor advisory
  49. 2026-08-30 05:29 UTCGHSA enrichment
  50. 2026-08-30 01:21 UTCEPSS rescore
  51. 2026-08-28 21:40 UTCEPSS rescore
  52. 2026-08-28 02:32 UTCVendor advisory
  53. 2026-08-28 02:32 UTCGHSA enrichment
  54. 2026-08-27 21:36 UTCEG score recompute
  55. 2026-08-27 21:36 UTCVendor advisory
  56. 2026-08-27 21:36 UTCGHSA enrichment
  57. 2026-08-27 14:24 UTCEPSS rescore
  58. 2026-08-27 14:01 UTCVendor advisory
  59. 2026-08-27 14:01 UTCGHSA enrichment
  60. 2026-08-27 03:58 UTCVendor advisory
  61. 2026-08-27 03:58 UTCGHSA enrichment
  62. 2026-08-27 00:14 UTCEG score recompute
  63. 2026-08-27 00:14 UTCVendor advisory
  64. 2026-08-27 00:14 UTCGHSA enrichment
  65. 2026-08-26 12:51 UTCVendor advisory
  66. 2026-08-26 12:51 UTCGHSA enrichment
  67. 2026-08-26 07:58 UTCVendor advisory
  68. 2026-08-26 07:58 UTCGHSA enrichment
  69. 2026-08-26 02:23 UTCVendor advisory
  70. 2026-08-26 02:23 UTCGHSA enrichment
  71. 2026-08-25 19:17 UTCVendor advisory
  72. 2026-08-25 19:17 UTCGHSA enrichment
  73. 2026-08-25 14:41 UTCEG score recompute
  74. 2026-08-25 14:41 UTCVendor advisory
  75. 2026-08-25 14:41 UTCGHSA enrichment

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-13221?
CVE-2026-13221 is a critical vulnerability published on July 13, 2026. Perl versions before 5.40.5-RC1, from 5.41.0 before 5.42.3-RC1, from 5.43.0 before 5.43.10 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…
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 September 8, 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 0% probability of exploitation in the next 30 days, which ranks it in the top 63.0% of all scored CVEs.
What is the CVSS score of CVE-2026-13221?
CVE-2026-13221 has a CVSS v3 base score of 9.1 (NVD).
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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