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CVE.org (no NVD analysis yet)· CNA GitHub_M

CVE-2026-92707: MessagePack: Nested arrays can blow past buffer length limits

Noroxi assessment

Priority: Monitor (action score 21/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.67% (FIRST EPSS); higher than 52.3% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: MessagePack 2.5.303 2.5.303; MessagePack 3.1.9 3.1.9; Microsoft Visual Studio 2022 version 17.14 17.14.42.

Low priority for now. Upgrade to MessagePack 2.5.303 2.5.303; MessagePack 3.1.9 3.1.9; Microsoft Visual Studio 2022 version 17.14 17.14.42 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.303 and 3.1.9, deserializing attacker-controlled MessagePack data as System.Object through PrimitiveObjectFormatter can cause excessive memory allocation. The formatter allocates an object[] from each declared array length before the configured object-graph depth limit rejects the input, while nested array headers can reuse the same trailing unread bytes to satisfy per-header length validation. A comparatively small payload can therefore keep many large arrays alive at once. When an attacker can submit such data repeatedly, the allocations can cause severe managed-heap pressure, excessive garbage collection, process termination, or loss of service. Exposure requires an application to deserialize untrusted data through the affected formatter path and permit repeated attacker-controlled submissions, such as a reachable ASP.NET Core SignalR hub method with an object parameter and AddMessagePackProtocol() enabled. This issue is fixed in versions 2.5.303 and 3.1.9.

MediumCVSS 5.3 · v3.1—No exploit Fix available
Published
Oct 15, 2026
Updated
Oct 16, 2026
EPSS
0.6% · 52th percentile

Report tools

JSON

Action score

21

Monitor

Low priority for now.

CVSS
21 / 40 · 5.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.6%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
5.3
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-92707

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • MessagePack-CSharp MessagePack-CSharp

    • < 2.5.303, >= 3.0.0, < 3.1.9affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10aspnetcore-runtime-10.0before 10.0.13-1.el10_210.0.13-1.el10_2
AlmaLinux:10aspnetcore-runtime-8.0before 8.0.32-1.el10_28.0.32-1.el10_2
AlmaLinux:10aspnetcore-runtime-9.0before 9.0.21-1.el10_29.0.21-1.el10_2
AlmaLinux:10aspnetcore-runtime-dbg-10.0before 10.0.13-1.el10_210.0.13-1.el10_2
AlmaLinux:10aspnetcore-runtime-dbg-8.0before 8.0.32-1.el10_28.0.32-1.el10_2
AlmaLinux:10aspnetcore-runtime-dbg-9.0before 9.0.21-1.el10_29.0.21-1.el10_2
AlmaLinux:10aspnetcore-targeting-pack-10.0before 10.0.13-1.el10_210.0.13-1.el10_2
AlmaLinux:10aspnetcore-targeting-pack-8.0before 8.0.32-1.el10_28.0.32-1.el10_2
AlmaLinux:10aspnetcore-targeting-pack-9.0before 9.0.21-1.el10_29.0.21-1.el10_2
AlmaLinux:10dotnet-apphost-pack-10.0before 10.0.13-1.el10_210.0.13-1.el10_2
AlmaLinux:10dotnet-apphost-pack-8.0before 8.0.32-1.el10_28.0.32-1.el10_2
AlmaLinux:10dotnet-apphost-pack-9.0before 9.0.21-1.el10_29.0.21-1.el10_2
AlmaLinux:10dotnet-hostbefore 10.0.13-1.el10_210.0.13-1.el10_2
AlmaLinux:10dotnet-hostfxr-10.0before 10.0.13-1.el10_210.0.13-1.el10_2
AlmaLinux:10dotnet-hostfxr-8.0before 8.0.32-1.el10_28.0.32-1.el10_2
AlmaLinux:10dotnet-hostfxr-9.0before 9.0.21-1.el10_29.0.21-1.el10_2
AlmaLinux:10dotnet-runtime-10.0before 10.0.13-1.el10_210.0.13-1.el10_2
AlmaLinux:10dotnet-runtime-8.0before 8.0.32-1.el10_28.0.32-1.el10_2
AlmaLinux:10dotnet-runtime-9.0before 9.0.21-1.el10_29.0.21-1.el10_2
AlmaLinux:10dotnet-runtime-dbg-10.0before 10.0.13-1.el10_210.0.13-1.el10_2
AlmaLinux:10dotnet-runtime-dbg-8.0before 8.0.32-1.el10_28.0.32-1.el10_2
AlmaLinux:10dotnet-runtime-dbg-9.0before 9.0.21-1.el10_29.0.21-1.el10_2
AlmaLinux:10dotnet-sdk-10.0before 10.0.113-1.el10_210.0.113-1.el10_2
AlmaLinux:10dotnet-sdk-10.0-source-built-artifactsbefore 10.0.113-1.el10_210.0.113-1.el10_2

+96

Same product

messagepack-csharp: all records

Other highest-scoring records for the same primary product.

  • CVE-2024-48924MessagePack allows untrusted data to lead to DoS attack due to hash collisions and stack overflow
    34Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
MessagePack 2.5.3032.5.303 · Release NotesMicrosoft (MSRC)
MessagePack 3.1.93.1.9 · Release NotesMicrosoft (MSRC)
Microsoft Visual Studio 2022 version 17.1417.14.42 · Release NotesMicrosoft (MSRC)
Microsoft Visual Studio 2026 version 18.1018.10.4 · Release NotesMicrosoft (MSRC)
Microsoft.AspNetCore.SignalR.Protocols.MessagePack on .NET 10.0 runtime installed on Linux10.0.13 · Release NotesMicrosoft (MSRC)
Microsoft.AspNetCore.SignalR.Protocols.MessagePack on .NET 10.0 runtime installed on Mac OS10.0.13 · Release NotesMicrosoft (MSRC)
Microsoft.AspNetCore.SignalR.Protocols.MessagePack on .NET 10.0 runtime installed on Windows10.0.13 · Release NotesMicrosoft (MSRC)
Microsoft.AspNetCore.SignalR.Protocols.MessagePack on .NET 11.0 runtime installed on Linux11.0.0-rc.2 · Release NotesMicrosoft (MSRC)
Microsoft.AspNetCore.SignalR.Protocols.MessagePack on .NET 11.0 runtime installed on Mac OS11.0.0-rc.2 · Release NotesMicrosoft (MSRC)
Microsoft.AspNetCore.SignalR.Protocols.MessagePack on .NET 11.0 runtime installed on Windows11.0.0-rc.2 · Release NotesMicrosoft (MSRC)
Microsoft.AspNetCore.SignalR.Protocols.MessagePack on .NET 8.0 runtime installed on Linux8.0.32 · Release NotesMicrosoft (MSRC)
Microsoft.AspNetCore.SignalR.Protocols.MessagePack on .NET 8.0 runtime installed on Mac OS8.0.32 · Release NotesMicrosoft (MSRC)
Microsoft.AspNetCore.SignalR.Protocols.MessagePack on .NET 8.0 runtime installed on Windows8.0.32 · Release NotesMicrosoft (MSRC)
Microsoft.AspNetCore.SignalR.Protocols.MessagePack on .NET 9.0 runtime installed on Linux9.0.21 · Release NotesMicrosoft (MSRC)
Microsoft.AspNetCore.SignalR.Protocols.MessagePack on .NET 9.0 runtime installed on Mac OS9.0.21 · Release NotesMicrosoft (MSRC)
Microsoft.AspNetCore.SignalR.Protocols.MessagePack on .NET 9.0 runtime installed on Windows9.0.21 · Release NotesMicrosoft (MSRC)
almalinux:aspnetcore-runtime-8.08.0.32-1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:aspnetcore-runtime-dbg-8.08.0.32-1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:aspnetcore-targeting-pack-8.08.0.32-1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:dotnet-apphost-pack-8.08.0.32-1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:dotnet-hostfxr-8.08.0.32-1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:dotnet-runtime-8.08.0.32-1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:dotnet-runtime-dbg-8.08.0.32-1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:dotnet-sdk-8.08.0.132-1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:dotnet-sdk-8.0-source-built-artifacts8.0.132-1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:dotnet-sdk-dbg-8.08.0.132-1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:dotnet-targeting-pack-8.08.0.32-1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:dotnet-templates-8.08.0.132-1.el10_2 · AlmaLinux:10Package registry (OSV)
NuGet:MessagePack2.5.303Package registry (OSV)
NuGet:MessagePack3.1.9Package registry (OSV)

+3

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 3, 2026+19 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
low · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
Low

Weakness class (CWE)

CWE-1325 · Improperly Controlled Sequential Memory Allocation

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓
  2. SSVC exploitation— → none
  3. Exploit maturity— → none

For records you follow, these changes also arrive as notifications. →

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records