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SCA: security update for MessagePack (GHSA-2x83-8g95-xh59)

medium Tenable Cloud Security Plugin ID 443967

Description

There are packages installed that are affected by a vulnerability referenced in the following CVE:

 - MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7,
 ExpandoObjectFormatter.Deserialize populates System.Dynamic.ExpandoObject by calling IDictionary<string,
 object>.Add for each map entry. ExpandoObject internally maintains member names in array-like structures,
 so inserting many distinct keys can require repeated linear scans and array copies. For large attacker-
 controlled maps, this produces quadratic CPU and allocation behavior. The issue is especially surprising
 because ExpandoObjectResolver.Options is configured with MessagePackSecurity.UntrustedData, but collision-
 resistant dictionary comparers cannot protect ExpandoObject insertion internals. This vulnerability is
 fixed in 2.5.301 and 3.1.7. (CVE-2026-48511)

Solution

Update the MessagePack library and its related packages to version 2.5.301 or later.

See Also

https://github.com/advisories/GHSA-2x83-8g95-xh59

Plugin Details

Severity: Medium

ID: 443967

Version: Revision 1.2

Type: Local

Family: SCA Checks

Published: 6/26/2026

Updated: 7/6/2026

Supported Sensors: Tenable Cloud Security, Tenable Self-Hosted Container Security

Risk Information

VPR

Risk Factor: Low

Score: 3

Percentile: 23.73

Vendor

Vendor Severity: Medium

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 5.8

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C

CVSS Score Source: CVE-2026-48511

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

CVSS v4

Risk Factor: Medium

Base Score: 6.3

Threat Score: 1.7

Threat Vector: CVSS:4.0/E:U

Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

Vulnerability Information

Exploit Ease: No known exploits are available

Patch Publication Date: 6/25/2026

Vulnerability Publication Date: 6/22/2026

Reference Information

CVE: CVE-2026-48511

cwe: CWE-407