CVE-2026-48509

CRITICALNVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.1 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 85% 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
9.1
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 9.1Exploit: NoneExposed: 0

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

MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, the parameterless MessagePackInputFormatter() constructor uses default serializer options, which resolve to MessagePackSerializerOptions.Standard with MessagePackSecurity.TrustedData. The formatter is designed for ASP.NET Core MVC request bodies, which commonly cross an HTTP trust boundary. This insecure default can expose applications to denial-of-service attacks that MessagePackSecurity.UntrustedData is intended to mitigate, such as hash-collision attacks against dictionary-like model properties. This vulnerability is fixed in 2.5.301 and 3.1.7.

CVSS v3
9.1
EG Score
9.1(medium)
EPSS
14.5%
KEV
Not listed

Published

June 22, 2026

Last Modified

June 25, 2026

Advisory Details (1)

Auto-updated Jun 23, 2026
Patch available. Sources: github.
github Patch Available

ASP.NET Core MessagePackInputFormatter defaults to TrustedData for HTTP request bodies · Advisory · MessagePack-CSharp/MessagePack-CSharp · GitHub

https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-2f33-pr97-265q

Vendor Advisories for CVE-2026-48509(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 50× in last 7d / 102× 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 102 total refreshes for this CVE.

  1. 2026-07-07 04:04 UTCEG score recompute
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  3. 2026-07-06 20:29 UTCEG score recompute
  4. 2026-07-06 16:27 UTCEPSS rescore
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  1. 2026-07-03 18:28 UTCEG score recompute
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  72. 2026-06-23 23:22 UTCEG score recompute▲ 2.80
  73. 2026-06-23 21:33 UTCEPSS rescore
  74. 2026-06-23 21:33 UTCEPSS rescore
  75. 2026-06-23 17:33 UTCNVD updateCVSS v3 → 9.1 · severity → CRITICAL

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-48509?
CVE-2026-48509 is a critical vulnerability published on June 22, 2026. MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, the parameterless MessagePackInputFormatter() constructor uses default serializer options, which resolve to MessagePackSerializerOptions.Standard with MessagePackSecurity.TrustedData. The formatter is designed for…
When was CVE-2026-48509 disclosed?
CVE-2026-48509 was first published in the National Vulnerability Database on June 22, 2026, with the most recent update on June 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-48509 actively exploited?
CVE-2026-48509 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 14.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-48509?
CVE-2026-48509 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2026-48509?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-48509, 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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