How severe is CVE-2026-48506?

CVE-2026-48506 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-48506 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (19th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-48506?

CVE-2026-48506 affects Messagepack. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-48506?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-48506 have an EU (EUVD) identifier?

Yes. CVE-2026-48506 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38388.

When was CVE-2026-48506 published?

CVE-2026-48506 was published on 2026-06-22 and last updated on 2026-06-23.

CVE-2026-48506

CVE-2026-48506 is a high-severity vulnerability in Messagepack with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-674.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (19th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-38388
Weakness: CWE-674
Affected product: Messagepack
Published: 2026-06-22
Last modified: 2026-06-23

Description

MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePackReader.TrySkip() recursively descends into nested arrays and maps without incrementing the reader depth or calling the configured depth checks. This bypasses MessagePackSecurity.MaximumObjectGraphDepth, the library's documented protection against deeply nested object graphs. Many generated and dynamic formatters call reader.Skip() when they encounter unknown map keys, unknown array members, ignored fields, or data that should be skipped for forward compatibility. A deeply nested value in one of these skipped positions can therefore cause unbounded recursion and an uncatchable StackOverflowException. This vulnerability is fixed in 2.5.301 and 3.1.7.

Frequently asked questions

What is CVE-2026-48506?: MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePackReader.TrySkip() recursively descends into nested arrays and maps without incrementing the reader depth or calling the configured depth checks. This bypasses MessagePackSecurity.MaximumObjectGraphDepth, the library's documented protection against deeply nested object graphs. Many generated and dynamic formatters call reader.Skip() when they encounter unknown map keys, unknown array members, ignored fields, or data that should be skipped for forward compatibility. A deeply nested value in one of these skipped positions can therefore cause unbounded recursion and an uncatchable StackOverflowException. This vulnerability is fixed in 2.5.301 and 3.1.7.
How severe is CVE-2026-48506?: CVE-2026-48506 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-48506 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (19th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-48506?: CVE-2026-48506 affects Messagepack. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-48506?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-48506 have an EU (EUVD) identifier?: Yes. CVE-2026-48506 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38388.
When was CVE-2026-48506 published?: CVE-2026-48506 was published on 2026-06-22 and last updated on 2026-06-23.

References

https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-vh6j-jc39-fggf

Affected products (1)

cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\#:*:*

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