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Fencer Intel
high 7.5

CVE-2026-108859 json

mcp-go through 1.2.1 Denial of Service via Unbounded POST Body Buffering

published 29d ago modified 22d ago also EUVD-2026-97010

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 46%
public exploits
0
none known

Summary

mcp-go through 1.2.1 contains a denial of service vulnerability in StreamableHTTPServer.ServeHTTP that allows remote unauthenticated attackers to exhaust memory by sending oversized POST bodies. Attackers can send arbitrarily large or many concurrent POST requests, read fully via io.ReadAll before validation, to degrade or OOM-kill the server process.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-108859 updated cvss 7.5

github.com/mark3labs/mcp-go: mcp-go: Denial of Service via unbounded HTTP request body buffering

  • Red Hat Hardened Images tempo3.0 3.0.3-0.4.hum1, tempo2.10 2.10.8-0.4.hum1
    affected: workaround, no fix available
  • Red Hat OpenShift distributed tracing 3.11 rhosdt/tempo-rhel9 1792610881, rhosdt/tempo-query-rhel9 1792610888
    fixed: vendor fix RHSA-2026:88187
  • Red Hat Connectivity Link 1 rhcl-tech-preview/mcp-gateway-rhel9, rhcl-tech-preview/mcp-gateway-rhel9-operator
    not affected: vulnerable code not present
  • Red Hat OpenShift AI (RHOAI) rhoai/rhai-cli-rhel9
    not affected: vulnerable code not in execute path
  • Red Hat OpenShift distributed tracing 3.11 rhosdt/tempo-gateway-rhel9 1792610901, rhosdt/tempo-rhel9-operator 1792610900, rhosdt/tempo-operator-bundle 1792660298, rhosdt/tempo-gateway-opa-rhel9 1792610843, rhosdt/tempo-jaeger-query-rhel9 1792610901
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
22d ago

Exploit prediction

0.55% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • mark3labs mcp-go

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.