How severe is CVE-2026-48514?

CVE-2026-48514 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-2026-48514 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-48514?

CVE-2026-48514 affects Messagepack. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-48514?

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-2026-48514 have an EU (EUVD) identifier?

Yes. CVE-2026-48514 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38382.

When was CVE-2026-48514 published?

CVE-2026-48514 was published on 2026-06-22 and last updated on 2026-06-25.

CVE-2026-48514

CVE-2026-48514 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-770.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 6.3
EPSS exploit prediction: 0% (14th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-38382
Weakness: CWE-770
Affected product: Messagepack
Published: 2026-06-22
Last modified: 2026-06-25

Description

MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, UnsafeBlitFormatterBase<T>.Deserialize reads an attacker-controlled byteLength from an extension payload and allocates an array based on that value before validating it against the extension header length or remaining payload bytes. The outer extension header is bounded by available input, but that bound is not used to constrain the inner byteLength before allocation. A very small payload can therefore request a very large T[] allocation. This vulnerability is fixed in 2.5.301 and 3.1.7.

Frequently asked questions

What is CVE-2026-48514?: MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, UnsafeBlitFormatterBase<T>.Deserialize reads an attacker-controlled byteLength from an extension payload and allocates an array based on that value before validating it against the extension header length or remaining payload bytes. The outer extension header is bounded by available input, but that bound is not used to constrain the inner byteLength before allocation. A very small payload can therefore request a very large T[] allocation. This vulnerability is fixed in 2.5.301 and 3.1.7.
How severe is CVE-2026-48514?: CVE-2026-48514 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-2026-48514 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-48514?: CVE-2026-48514 affects Messagepack. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-48514?: 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-2026-48514 have an EU (EUVD) identifier?: Yes. CVE-2026-48514 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38382.
When was CVE-2026-48514 published?: CVE-2026-48514 was published on 2026-06-22 and last updated on 2026-06-25.

References

https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-w567-gjr2-hm5j

Affected products (1)

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

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