Medium

CVE-2026-115845 — Incomplete validation in the run_script Python sandbox in AWS MCP Server

An incomplete list of disallowed inputs in the Python code validator of the run_script tool in AWS MCP Server might allow an authenticated remote user to execute arbitrary code within their own isolated session environment via a crafted script. AWS fixed this issue service-side. No customer action is required.

Published Oct 23, 2026 · Updated Oct 23, 2026 · Sources: CVE Program (cve.org) e CISA ADP, NIST National Vulnerability Database · CNA: AMZN

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.3% (30-day exploitation probability)+4
Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.31%

ahead of 23% of scored CVEs · Oct 29, 2026

Affects

AWS

AWS MCP Server

CVSS base

6.4

Medium · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (AWS AWS MCP Server).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
AWS	AWS MCP Server	version N/A	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
5.3	CVSS 4.0	Medium	—	—	ff89ba41-3aa1-4d27-914a-91399e9639e5 via NIST National Vulnerability Database
5.3	CVSS 4.0	Medium	—	—	AMZN via CVE Program (cve.org) e CISA ADP
6.4	CVSS 3.1	Medium	3.1	2.7	ff89ba41-3aa1-4d27-914a-91399e9639e5 via NIST National Vulnerability Database
6.4	CVSS 3.1	Medium	—	—	AMZN via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N (score shown at the top: ff89ba41-3aa1-4d27-914a-91399e9639e5)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-184

Other CVEs with this weakness →

EPSS over time FIRST

Oct 24, 2026 → Oct 29, 2026 · 6 reading(s) · max 0.38%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

2026
Source status changed · Published → Awaiting Analysis
Oct 23, 2026 · NIST National Vulnerability Database
Record published
Oct 23, 2026
CVSS changed · 6.4
Oct 23, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Published
Oct 23, 2026 · CVE Program (cve.org) e CISA ADP
Record created in this database
Oct 23, 2026 · CVE Program (cve.org) e CISA ADP
CVE published
Oct 23, 2026 · AMZN

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 23, 2026 – Oct 23, 2026

References

1 on the record

aws.amazon.com/security/security-bulletins/2026-149-aws/
vendor-advisory, CVE Program (cve.org) e CISA ADP

Elsewhere on this site

AWS
every CVE for this vendor

CWE-184
other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-115845 is "Incomplete validation in the run_script Python sandbox in AWS MCP Server", rated Medium. It affects AWS MCP Server (AWS); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.4 describes technical severity. EPSS 0.31% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

Comments

Moderated technical discussion. Read the community guidelines.

No comments yet.