CVE-2026-81887

MEDIUMPre-NVD 5.15.1—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 58% 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, secondary
5.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 5.1Exploit: None knownExposed: 0

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

Livewire is a full-stack framework for Laravel. From 3.0.0-beta.1 until 3.8.3 and 4.3.4, the dot-notated query-string parser in js/plugins/history/index.js, including fromQueryString() and insertDotNotatedValueIntoData(), accepts the __proto__, constructor, and prototype path segments and creates inherited objects. Client-side state handlers then access effects.html, effects.js, effects.xjs, and effects.scripts without Object.prototype.hasOwnProperty.call(), allowing inherited attacker-controlled state to be treated as trusted effects. An unauthenticated attacker can craft a URL that, when opened by a user, executes arbitrary JavaScript in the affected application's origin. Exploitation requires user interaction and does not bypass server-side authorization or grant privileges beyond the affected user. This issue is fixed in versions 3.8.3 and 4.3.4.

CVSS v3
5.1
EG Score
5.1(medium)
EG Risk
23(Track)
EG Risk 23/100SSVC: 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
Severity51% × 45%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
42%
KEV
Not listed

Published

August 31, 2026

Last Modified

September 9, 2026

Advisory Details (5)

Auto-updated Aug 31, 2026
Patch available. Sources: github, github_pr, github_commit, github_release.
github_release Patch Available

v4.3.4

Patch available: livewire/livewire v4.3.4

https://github.com/livewire/livewire/releases/tag/v4.3.4
github_release Patch Available

v3.8.3

Patch available: livewire/livewire v3.8.3

https://github.com/livewire/livewire/releases/tag/v3.8.3
github_commit Patch Available

commit 11ebe646f7e8 (livewire/livewire)

Patch available: livewire/livewire v3.8.3 (contains commit 11ebe646f7e8)

https://github.com/livewire/livewire/commit/11ebe646f7e81dde2d714815da8b3019d058561e
github_pr Patch Available

[3.x] Improve query string parsing and effect handling

Patch available: livewire/livewire v3.8.3 (PR #10467 merged 2026-07-30)

https://github.com/livewire/livewire/pull/10467
github Patch Available

Livewire DOM-based cross-site scripting during client-side state handling · Advisory · livewire/livewire · GitHub

https://github.com/livewire/livewire/security/advisories/GHSA-g3hc-697w-wm82

Vendor Advisories for CVE-2026-81887(1)

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

Affected Packages

(1 across 1 ecosystem)
Packagist(1)
PackageVulnerable rangeFixed inDependents
livewire/livewirev4.0.0 ... v4.3.3 (25 versions)4.3.4—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 34× 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. 2026-09-19 21:04 UTCEG score recompute
  2. 2026-09-18 21:26 UTCEG score recompute
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-17 20:47 UTCEG score recompute
  5. 2026-09-16 18:44 UTCEG score recompute
  6. 2026-09-16 14:08 UTCEPSS rescore
  7. 2026-09-16 05:15 UTCEPSS rescore
  8. 2026-09-15 18:53 UTCEG score recompute
  9. 2026-09-15 03:12 UTCEPSS rescore
  10. 2026-09-15 03:12 UTCEPSS rescore
  11. 2026-09-13 19:39 UTCEG score recompute
  12. 2026-09-12 20:02 UTCEG score recompute
  13. 2026-09-11 20:25 UTCEG score recompute
  14. 2026-09-11 14:53 UTCEPSS rescore
  15. 2026-09-11 14:53 UTCEPSS rescore
  16. 2026-09-10 20:48 UTCEG score recompute
  17. 2026-09-08 23:29 UTCEG score recompute
  18. 2026-09-08 22:01 UTCEPSS rescore
  19. 2026-09-07 17:52 UTCEG score recompute
  20. 2026-09-06 18:15 UTCEG score recompute
  21. 2026-09-06 13:48 UTCEPSS rescore
  22. 2026-09-05 18:38 UTCEG score recompute
  23. 2026-09-05 15:31 UTCEPSS rescore
  24. 2026-09-04 19:01 UTCEG score recompute
  25. 2026-09-04 05:07 UTCEPSS rescore
Show 9 more
  1. 2026-09-03 19:23 UTCEG score recompute
  2. 2026-09-03 18:37 UTCEG score recompute
  3. 2026-09-02 20:42 UTCEG score recompute
  4. 2026-09-02 14:12 UTCEPSS rescore
  5. 2026-09-01 21:06 UTCEG score recompute
  6. 2026-09-01 13:54 UTCEPSS rescore
  7. 2026-08-31 21:22 UTCEG score recompute
  8. 2026-08-31 20:21 UTCEG score recompute
  9. 2026-08-31 20:21 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-81887?
CVE-2026-81887 is a medium vulnerability published on August 31, 2026. Livewire is a full-stack framework for Laravel. From 3.0.0-beta.1 until 3.8.3 and 4.3.4, the dot-notated query-string parser in js/plugins/history/index.js, including fromQueryString() and insertDotNotatedValueIntoData(), accepts the proto, constructor, and prototype path segments and creates…
When was CVE-2026-81887 disclosed?
CVE-2026-81887 was first published in the National Vulnerability Database on August 31, 2026, with the most recent update on September 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-81887 actively exploited?
CVE-2026-81887 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 58.2% of all scored CVEs.
What is the CVSS score of CVE-2026-81887?
CVE-2026-81887 has a CVSS v3 base score of 5.1 (NVD).
How do I remediate CVE-2026-81887?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-81887, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-81887

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