How severe is CVE-2026-48513?

CVE-2026-48513 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-2026-48513 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-2026-48513?

CVE-2026-48513 affects Messagepack. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-48513?

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-2026-48513 have an EU (EUVD) identifier?

Yes. CVE-2026-48513 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38383.

When was CVE-2026-48513 published?

CVE-2026-48513 was published on 2026-06-22 and last updated on 2026-06-25.

CVE-2026-48513

CVE-2026-48513 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)
CVSS v4: 6.3
EPSS exploit prediction: 0% (14th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-38383
Weakness: CWE-674
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, runtime-generated union deserializers emitted by DynamicUnionResolver do not call MessagePackSecurity.DepthStep(ref reader) and do not decrement reader.Depth around recursive deserialization and skip paths. This means union deserialization does not consistently participate in the maximum object graph depth enforcement that protects other recursive formatter paths. For unknown union keys, the emitted deserializer calls reader.Skip() on attacker-controlled data without an enclosing depth step. This vulnerability is fixed in 2.5.301 and 3.1.7.

Frequently asked questions

What is CVE-2026-48513?: MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, runtime-generated union deserializers emitted by DynamicUnionResolver do not call MessagePackSecurity.DepthStep(ref reader) and do not decrement reader.Depth around recursive deserialization and skip paths. This means union deserialization does not consistently participate in the maximum object graph depth enforcement that protects other recursive formatter paths. For unknown union keys, the emitted deserializer calls reader.Skip() on attacker-controlled data without an enclosing depth step. This vulnerability is fixed in 2.5.301 and 3.1.7.
How severe is CVE-2026-48513?: CVE-2026-48513 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-2026-48513 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-2026-48513?: CVE-2026-48513 affects Messagepack. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-48513?: 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-2026-48513 have an EU (EUVD) identifier?: Yes. CVE-2026-48513 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38383.
When was CVE-2026-48513 published?: CVE-2026-48513 was published on 2026-06-22 and last updated on 2026-06-25.

References

https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-wfr3-xj75-pfwh

Affected products (1)

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

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