Which versions of OpenStack Swift are affected by CVE-2026-49017?

OpenStack Swift's s3api middleware (versions 2.36.0-2.36.1, 2.37.0-2.37.1) contains a denial-of-service vulnerability that allows authenticated S3 API users to permanently disable proxy-server…. A patch is available.

How to fix or mitigate CVE-2026-49017?

Within 24 hours: inventory all Swift deployments running affected versions (2.36.0-2.36.1, 2.37.0-2.37.1). Within 7 days: apply vendor patches (upgrade to Swift 2.36.2 or 2.37.2). Within 30 days: complete rollout across all environments and validate proxy-server stability under operational load.

OpenStack Swift CVE-2026-49017

Q: What is the CVSS score of CVE-2026-49017?

CVE-2026-49017 has a CVSS 4.0 base score of 7.1 (High). CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/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. EPSS exploitation probability: 0.0%.

EUVD-2026-32040 HIGH

Loop with Unreachable Exit Condition (Infinite Loop) (CWE-835)

2026-05-27 mitre

GHSA-g7jq-j257-rww2

Denial Of Service Swift Red Hat

7.1

CVSS 4.0 · NVD

Severity by source

NVD PRIMARY

7.1 HIGH

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/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

Red Hat

6.5 MEDIUM

qualitative

Primary rating from NVD.

CVSS VectorNVD

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Lifecycle Timeline

Analysis Generated

May 27, 2026 - 20:37 vuln.today

DescriptionCVE.org

In OpenStack Swift before 2.36.2 and 2.37.2, s3api middleware enters an infinite loop when processing a truncated aws-chunked PUT request body. The StreamingInput class repeatedly appends an empty buffer and re-reads, causing the proxy-server worker handling the request to become permanently unresponsive with increasing CPU and memory consumption. An authenticated attacker can systematically exhaust all proxy-server workers, resulting in denial of service. The defect was introduced in Swift 2.36.0.

AnalysisAI

Denial of service in OpenStack Swift's s3api middleware allows an authenticated S3 API user to permanently hang proxy-server workers by sending a truncated aws-chunked PUT request body. Versions 2.36.0 through 2.36.1 and 2.37.0 through 2.37.1 are affected; the defect was introduced in 2.36.0 and fixed in 2.36.2 and 2.37.2. There is no public exploit identified at time of analysis, and EPSS is very low (0.04%, 12th percentile), but the high availability impact and low attack complexity make this a credible operational threat to S3-compatible Swift deployments.

Technical ContextAI

OpenStack Swift is a distributed object storage system; its s3api middleware provides an Amazon S3-compatible REST interface on the proxy-server tier. AWS chunked uploads (the aws-chunked content encoding) frame the request body into length-prefixed chunks that the StreamingInput class reads incrementally. The flaw is a CWE-835 (Loop with Unreachable Exit Condition / 'infinite loop'): when the chunked body is truncated, StreamingInput repeatedly appends an empty buffer and re-reads instead of detecting end-of-stream or erroring out, so the loop never terminates. The single CPE (cpe:2.3:a:openstack:swift) confirms the OpenStack Swift application package is the affected component, specifically the proxy-server worker process handling the malformed request.

RemediationAI

Vendor-released patch: upgrade to Swift 2.36.2 (for the 2.36.x line) or 2.37.2 (for the 2.37.x line), which contain the fix; deployments on 2.35.x and earlier are unaffected and do not regress. The corrective changes are tracked in Gerrit at https://review.opendev.org/c/openstack/swift/+/987957 and https://review.opendev.org/c/openstack/swift/+/988093, with background at https://bugs.launchpad.net/bugs/2152205 and the oss-security disclosure at http://www.openwall.com/lists/oss-security/2026/05/27/9. If immediate patching is not possible, compensating controls include disabling or restricting the s3api middleware in the proxy-server pipeline where the S3-compatible interface is not required (trade-off: breaks all S3 API clients), and placing a reverse proxy or WAF in front of the proxy-server to enforce request body completeness and Content-Length consistency for aws-chunked uploads (trade-off: chunked-encoding validation is non-trivial and may reject some legitimate streaming clients). Operationally, monitor proxy-server workers for stuck threads with rising CPU/memory and configure worker recycling/timeouts so hung workers are reaped, and rate-limit or revoke credentials of abusive authenticated clients (trade-off: does not close the root cause).