CVE-2026-33993

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 0.6%, top 55% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.8Exploit: None knownExposed: 0

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

Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. Prior to version 3.0.25, the unserialize() function in locutus/php/var/unserialize assigns deserialized keys to plain objects via bracket notation without filtering the __proto__ key. When a PHP serialized payload contains __proto__ as an array or object key, JavaScript's __proto__ setter is invoked, replacing the deserialized object's prototype with attacker-controlled content. This enables property injection, for...in propagation of injected properties, and denial of service via built-in method override. This is distinct from the previously reported prototype pollution in parse_str (GHSA-f98m-q3hr-p5wq, GHSA-rxrv-835q-v5mh) — unserialize is a different function with no mitigation applied. Version 3.0.25 patches the issue.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: 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
Severity98% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
47%
KEV
Not listed

Published

March 27, 2026

Last Modified

June 17, 2026

Advisory Details (4)

Auto-updated Sep 14, 2026
🔬 Proof of concept available. Patch available. Sources: github_pr, github_release, github, github_commit.
github Patch Available🟡 PoC Available

Prototype injection via \_\_proto\_\_ key in unserialize() enables property injection and method override on deserialized objects · Advisory · locutusjs/locutus · GitHub

https://github.com/locutusjs/locutus/security/advisories/GHSA-4mph-v827-f877
github_release Patch Available

v3.0.25

Patch available: locutusjs/locutus v3.0.25

https://github.com/locutusjs/locutus/releases/tag/v3.0.25
github_pr Patch Available

fix: harden php prototype pollution sinks

Patch available: locutusjs/locutus v3.0.25 (PR #597 merged 2026-03-25)

https://github.com/locutusjs/locutus/pull/597
github_commit Patch Available

commit 345a6211e1e6 (locutusjs/locutus)

Patch available: locutusjs/locutus v3.0.25 (contains commit 345a6211e1e6)

https://github.com/locutusjs/locutus/commit/345a6211e1e6f939f96a7090bfeff642c9fcf9e4

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
locutus—3.0.25—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 30× 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. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 19:28 UTCEPSS rescore
  3. 2026-09-17 19:30 UTCEPSS rescore
  4. 2026-09-16 14:08 UTCEPSS rescore
  5. 2026-09-16 05:15 UTCEPSS rescore
  6. 2026-09-15 03:11 UTCEPSS rescore
  7. 2026-09-13 16:47 UTCEPSS rescore
  8. 2026-09-12 15:01 UTCEPSS rescore
  9. 2026-09-11 14:53 UTCEPSS rescore
  10. 2026-09-11 09:37 UTCEPSS rescore
  11. 2026-09-10 09:34 UTCEPSS rescore
  12. 2026-09-08 22:00 UTCEPSS rescore
  13. 2026-09-07 16:01 UTCEPSS rescore
  14. 2026-09-06 13:47 UTCEPSS rescore
  15. 2026-09-04 05:06 UTCEPSS rescore
  16. 2026-09-02 14:12 UTCEPSS rescore
  17. 2026-09-02 13:04 UTCOSV refresh
  18. 2026-09-01 13:53 UTCEPSS rescore
  19. 2026-09-01 04:39 UTCEPSS rescore
  20. 2026-08-30 19:17 UTCEPSS rescore
  21. 2026-08-30 01:22 UTCEPSS rescore
  22. 2026-08-28 21:41 UTCEPSS rescore
  23. 2026-08-27 14:25 UTCEPSS rescore
  24. 2026-08-26 14:46 UTCEPSS rescore
  25. 2026-08-25 13:49 UTCEPSS rescore
Show 38 more
  1. 2026-08-24 14:17 UTCEPSS rescore
  2. 2026-08-23 00:19 UTCEPSS rescore
  3. 2026-08-21 23:49 UTCEPSS rescore
  4. 2026-08-20 22:55 UTCEPSS rescore
  5. 2026-08-20 22:55 UTCEPSS rescore
  6. 2026-08-19 17:03 UTCEPSS rescore
  7. 2026-08-18 13:48 UTCEPSS rescore
  8. 2026-08-17 13:47 UTCEPSS rescore
  9. 2026-08-16 14:56 UTCEPSS rescore
  10. 2026-08-16 09:55 UTCEG score recompute
  11. 2026-08-16 02:14 UTCEPSS rescore
  12. 2026-08-15 01:30 UTCEPSS rescore
  13. 2026-08-14 06:14 UTCEG score recompute
  14. 2026-08-13 22:00 UTCEPSS rescore
  15. 2026-08-12 20:33 UTCEG score recompute
  16. 2026-08-12 13:50 UTCEPSS rescore
  17. 2026-08-11 20:43 UTCEG score recompute
  18. 2026-08-11 03:43 UTCEG score recompute
  19. 2026-08-11 00:00 UTCEPSS rescore
  20. 2026-08-09 16:47 UTCEG score recompute
  21. 2026-08-09 13:46 UTCEPSS rescore
  22. 2026-08-09 05:48 UTCEG score recompute
  23. 2026-08-08 16:37 UTCEPSS rescore
  24. 2026-08-07 19:55 UTCEG score recompute
  25. 2026-08-06 18:33 UTCEG score recompute
  26. 2026-08-06 13:46 UTCEPSS rescore
  27. 2026-08-06 00:43 UTCEG score recompute
  28. 2026-08-05 19:17 UTCEPSS rescore
  29. 2026-08-04 15:10 UTCEPSS rescore
  30. 2026-08-04 10:38 UTCEPSS rescore
  31. 2026-08-03 23:05 UTCEG score recompute
  32. 2026-08-03 10:36 UTCEPSS rescore
  33. 2026-08-02 15:08 UTCEG score recompute
  34. 2026-08-02 02:27 UTCEPSS rescore
  35. 2026-08-01 04:16 UTCEPSS rescore
  36. 2026-07-30 16:28 UTCEPSS rescore
  37. 2026-07-30 01:30 UTCEPSS rescore
  38. 2026-07-27 14:19 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-33993?
CVE-2026-33993 is a critical vulnerability published on March 27, 2026. Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. Prior to version 3.0.25, the unserialize() function in locutus/php/var/unserialize assigns deserialized keys to plain objects via bracket notation without filtering the proto key. When a PHP serialized…
When was CVE-2026-33993 disclosed?
CVE-2026-33993 was first published in the National Vulnerability Database on March 27, 2026, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-33993 actively exploited?
CVE-2026-33993 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 53.5% of all scored CVEs.
What is the CVSS score of CVE-2026-33993?
CVE-2026-33993 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-33993?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-33993, 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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