CVE-2026-48502
CVE-2026-48502 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-125.
Key facts
- Severity: High (CVSS 3.x base score 7.5)
- CVSS v4: 8.2
- EPSS exploit prediction: 0% (17th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-38389
- Weakness: CWE-125
- Affected product: Messagepack
- Published:
- Last modified:
Description
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePackReader.ReadDateTime() can allocate stack memory based on an attacker-controlled MessagePack extension length. In the slow path for timestamp extension parsing, the computed tokenSize includes the extension body length from the wire and is used in a stackalloc operation before the extension length is validated as one of the valid timestamp sizes. A very small payload can claim a large timestamp extension body and cause a stack allocation large enough to trigger an uncatchable StackOverflowException, terminating the host process. This vulnerability is fixed in 2.5.301 and 3.1.7.
Frequently asked questions
- What is CVE-2026-48502?
- MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePackReader.ReadDateTime() can allocate stack memory based on an attacker-controlled MessagePack extension length. In the slow path for timestamp extension parsing, the computed tokenSize includes the extension body length from the wire and is used in a stackalloc operation before the extension length is validated as one of the valid timestamp sizes. A very small payload can claim a large timestamp extension body and cause a stack allocation large enough to trigger an uncatchable StackOverflowException, terminating the host process. This vulnerability is fixed in 2.5.301 and 3.1.7.
- How severe is CVE-2026-48502?
- CVE-2026-48502 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-2026-48502 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-48502?
- CVE-2026-48502 affects Messagepack. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2026-48502?
- 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-2026-48502 have an EU (EUVD) identifier?
- Yes. CVE-2026-48502 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38389.
- When was CVE-2026-48502 published?
- CVE-2026-48502 was published on 2026-06-22 and last updated on 2026-06-23.
References
Affected products (1)
- cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\#:*:*
More vulnerabilities in Messagepack
- CVE-2026-48509 — Critical (CVSS 9.1): MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, the parameterless…
- CVE-2026-48109 — High (CVSS 8.2): MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, A vulnerability exists in the…
- CVE-2026-48517 — High (CVSS 7.5): MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePack-CSharp's typeless…
- CVE-2026-48516 — High (CVSS 7.5): MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7,…
- CVE-2026-48515 — High (CVSS 7.5): MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePack-CSharp's…
- CVE-2026-48514 — High (CVSS 7.5): MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7,…
All CVEs affecting Messagepack →
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