CVE-2026-48516
CVE-2026-48516 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-407.
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-2026-38380
- Weakness: CWE-407
- 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, InterfaceLookupFormatter<TKey,TElement> constructs an internal Dictionary<TKey, IGrouping<TKey,TElement>> with the default equality comparer instead of the security-aware comparer supplied by options.Security.GetEqualityComparer<TKey>(). This formatter omission allows hash-collision CPU denial of service against ILookup<TKey,TElement> even when the application has opted into the untrusted-data security posture This vulnerability is fixed in 2.5.301 and 3.1.7.
Frequently asked questions
- What is CVE-2026-48516?
- MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, InterfaceLookupFormatter<TKey,TElement> constructs an internal Dictionary<TKey, IGrouping<TKey,TElement>> with the default equality comparer instead of the security-aware comparer supplied by options.Security.GetEqualityComparer<TKey>(). This formatter omission allows hash-collision CPU denial of service against ILookup<TKey,TElement> even when the application has opted into the untrusted-data security posture This vulnerability is fixed in 2.5.301 and 3.1.7.
- How severe is CVE-2026-48516?
- CVE-2026-48516 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-2026-48516 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-2026-48516?
- CVE-2026-48516 affects Messagepack. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2026-48516?
- 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-2026-48516 have an EU (EUVD) identifier?
- Yes. CVE-2026-48516 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38380.
- When was CVE-2026-48516 published?
- CVE-2026-48516 was published on 2026-06-22 and last updated on 2026-06-25.
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-2026-48515 — 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,…
- CVE-2026-48513 — High (CVSS 7.5): MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, runtime-generated union…
All CVEs affecting Messagepack →
Other CWE-407 vulnerabilities
- CVE-2026-58226 — High (CVSS 8.7): Inefficient Algorithmic Complexity vulnerability in elixir-mint hpax allows unauthenticated denial-of-service via…
- CVE-2026-54892 — High (CVSS 8.7): Inefficient algorithmic complexity in Plug's nested-parameter decoder allows an unauthenticated remote attacker to…
- CVE-2026-59094 — High (CVSS 7.5): Pathway through 0.31.1, fixed in commit d09722e, document store applies a caller-supplied glob pattern to indexed…
- CVE-2026-53433 — High (CVSS 7.5): fzf is vulnerable to a Denial of Service (DoS) due to inefficient HTTP body processing in the --listen mode due to…
- CVE-2026-13311 — High (CVSS 7.5): shell-quote prior to 1.8.5 finalizes parsed tokens in parse() using Array.prototype.concat as a reduce accumulator,…
- CVE-2026-48511 — High (CVSS 7.5): MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, ExpandoObjectFormatter.Deserialize…