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العربيةSelf-grant S3 read via bucket policy
Can rewrite a bucket's policy to grant itself read access, then read it.
Grants escalation on its own.
s3:PutBucketPolicyOn its own, s3:PutBucketPolicy can rewrite a bucket's policy to grant itself read access, then read it. On a wide resource scope that alone reaches access for an outside or public principal.
Why it is dangerous
A principal can call s3:PutBucketPolicy on the bucket to attach a resource policy granting itself (or the public) s3:GetObject, then read the bucket's objects. This bypasses the absence of an identity-policy read grant: the attacker rewrites the lock rather than holding a key. Severity is driven by the bucket's sensitivity - control of the policy becomes direct exfiltration of whatever the bucket holds.
In MITRE ATT&CK terms this maps to T1098, Account Manipulation, under the privilege escalation tactic. AWS records it in CloudTrail as PutBucketPolicy, PutBucketAcl, PutAccountPublicAccessBlock. The call shows up in CloudTrail but blends into normal administration, so it needs a rule to stand out.
Detection
PutBucketPolicyPutBucketAclPutAccountPublicAccessBlockPrerequisites
s3:PutBucketPolicy on the bucket. The abuse additionally assumes no SCP/boundary/PrincipalOrgID guardrail blocks the over-grant and (for a public grant) that account-level S3 Block Public Access is not enforcing.
MITRE ATT&CK
T1098 · Account ManipulationTactic
Privilege Escalation
A control that would remove it: Restrict s3:PutBucketPolicy to CI/CD/admins; enable account-level S3 Block Public Access; deny bucket-policy writes via SCP.
Whether to apply it depends on how the permission is used in your environment, so it is a business decision rather than an automatic fix. The same permission can be load-bearing in one account and pure risk in another.
Pathbreak confirms whether this path resolves in your account, ranks it against the others by how much it opens up, and uses your threat model and business context to show which paths are worth cutting.
Questions
What does s3:PutBucketPolicy allow?
Can rewrite a bucket's policy to grant itself read access, then read it.
Can s3:PutBucketPolicy escalate privileges on its own?
Yes. Held on a broad enough resource it reaches access for an outside or public principal with no other permission.
How is self-grant S3 read via bucket policy detected?
Watch for PutBucketPolicy, PutBucketAcl, PutAccountPublicAccessBlock in CloudTrail. The call shows up in CloudTrail but blends into normal administration, so it needs a rule to stand out.
How do you break this path?
A control that would remove it is: Restrict s3:PutBucketPolicy to CI/CD/admins; enable account-level S3 Block Public Access; deny bucket-policy writes via SCP. Whether to apply it depends on how the permission is used in your account, so it is a business decision rather than an automatic fix.
Which MITRE ATT&CK technique is this?
T1098, Account Manipulation, under the privilege escalation tactic.
Related paths
References
Find this in your own account
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