# CVE-2026-103957 — AWS loom

> As of 2026-10-09, CVE-2026-103957 is a MEDIUM-severity vulnerability in AWS loom, CVSS v3.1 6.2, EPSS 0.3% (29.7th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-103957, most recently “AWS AI Agent Vulnerabilities (Loom, SageMaker Unified Studio) Let Attackers Bypass Authentication and Steal Credentials - CVE-2026-103956, CVE-2026-103957, CVE-2026-103958, CVE-2026-104019”.

**Last updated:** 2026-10-09

## What is CVE-2026-103957?

Server-side request forgery in the OAuth2 discovery handling in Loom for AWS before 1.7.0 might allow an authenticated remote user to obtain the access token of another user of the deployment and to cause the application to issue requests to arbitrary internal network locations, via a crafted discovery document address supplied when registering a tool server or remote agent configured for delegated authentication. To remediate this issue, users should upgrade to version 1.7.0 or later.

The record classifies CVE-2026-103957 under weakness classes [CWE-918](https://intel.threadlinqs.com/cwe/CWE-918), [CWE-201](https://cwe.mitre.org/data/definitions/201.html). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs high-privilege credentials, needs a user to take an action first, and has high impact on confidentiality. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 22 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 6.2 — MEDIUM (`CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:N/A:N`)
- **CVSS v4.0 base score:** 8.2 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N`)
- **EPSS (FIRST):** 0.3% probability of exploitation in the next 30 days, higher than 29.7% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-10-02, last modified 2026-10-09

## Is CVE-2026-103957 being exploited?

It currently carries a trending score of 40 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [AWS](https://intel.threadlinqs.com/vendors/aws): loom

## How to fix CVE-2026-103957

No vendor patch reference has been recorded for CVE-2026-103957 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-103957

1 tracked threat in the Threadlinqs corpus references CVE-2026-103957, either in the campaign’s CVE list or as an indicator on the campaign record.

- [AWS AI Agent Vulnerabilities (Loom, SageMaker Unified Studio) Let Attackers Bypass Authentication and Steal Credentials - CVE-2026-103956, CVE-2026-103957, CVE-2026-103958, CVE-2026-104019](https://intel.threadlinqs.com/threat/TL-2026-2860) — CRITICAL · 2026-10-03

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-10-10. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com — release notes](https://github.com/awslabs/loom/releases/tag/v1.7.0)
- [aws.amazon.com — vendor advisory](https://aws.amazon.com/security/security-bulletins/2026-124-aws/)

**Third-party advisory**

- [github.com — third party advisory](https://github.com/awslabs/loom/security/advisories/GHSA-jcxf-gpf4-58hm)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-103957
Full detection coverage and IOCs for threats exploiting CVE-2026-103957 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp