8.7

CVE-2026-108859: mcp-go through 1.2.1 Denial of Service via Unbounded POST Body Buffering

Deferred
Published 11-10-2026Last modified 18-10-2026

Vulnerability summary

CVE-2026-108859 is a high (CVSS 8.7) vulnerability in mark3labs mcp-go. EPSS estimates a 0.55% chance of exploitation in the next 30 days, higher than 45.8% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 8.7 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 1% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
8.7/10
010
High · v4.0 (CVE.org)
EPSS score
0.55%
0%100%
Low · Change unavailable
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 11-10-2026
    PublishedVulnerability first disclosed.
  2. 18-10-2026
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

4 scores · 2 sources · 2 versions

EPSS trend

Probability

0.55%

Chance of exploitation in the next 30 days

Percentile

46%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

12-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Mark3labs1 product

1 vendor · 1 product

References

4 links