Server-side request forgery in the Session Manager port forwarding functionality in AWS Systems Manager Agent

published 2026-09-10 59 d ago modified 2026-09-10 59 d ago also EUVD-2026-75674

cvss: 9.9; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.7%; EPSS 0.7% chance of exploitation in 30 days, percentile 51%
public exploits: 0; none known

A server-side request forgery issue due to improper validation of equivalent address representations in the port forwarding to remote hosts functionality in Amazon AWS Systems Manager Agent (SSM Agent) before 3.3.4851.0 on all platforms might allow an authenticated remote user to bypass the remote destination denylist and reach link-local endpoints, potentially obtaining the temporary IAM role credentials of a managed instance and acting with that role's permissions from outside the instance, via a crafted destination host value that uses an alternate representation of a denied link-local address.

To remediate this issue, users should upgrade to version 3.3.4851.0 or later.

Patch / fix

fixed in 1 links 1

AWS Amazon SSM Agent 3.3.4851.0

github.com/aws/amazon-ssm-agent/releases/tag/3.3.4851.0 release

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 59 d ago (2026-09-10)

Exploit prediction

0.66% chance of exploitation in the next 30 days, higher than 51% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	9.9	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CNA	4.0	8.5	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:H
CNA	4.0	8.5	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:H/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

AWS Amazon SSM Agent

Classification

Weakness

CWE-918 Server-Side Request Forgery
CWE-1289 Improper Validation of Unsafe Equivalence in Input

References

github.com /aws/amazon-ssm-agent/releases/tag/3.3.4851.0
patch
aws.amazon.com /security/security-bulletins/2026-107-aws/
vendor-advisory
github.com /aws/amazon-ssm-agent/security/advisories/GHSA-w9jw-h72g-6hxc
third-party-advisory

Sources

CVE List CVE-2026-89049
NVD CVE-2026-89049

Fencer Vulns 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.

Summary