CVE-2026-71190 - Vulnerability Details

- openstack-swift: openstack-swift: Unauthenticated denial of service via catastrophic backtracking in Accept header parser

Description

In OpenStack Swift through 2.38.0, the proxy server Accept header parser contains a regular expression vulnerable to catastrophic backtracking (ReDoS). The "qdtext" pattern (?:[^"]|\\.)* allows an unauthenticated remote attacker to send a crafted Accept header that causes exponential CPU consumption in the proxy worker. A payload of 32 backslash-character pairs exceeds 30 seconds of CPU time. No authentication is required. Repeated requests can exhaust all proxy worker threads, resulting in a complete denial of service.

Published: 2026-08-05

Score: 8.7 High

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Impact

The vulnerability is a catastrophic back‑tracking bug in OpenStack Swift's proxy server Accept header parser. A specially crafted Accept header containing many back‑slash pairs forces the regular expression (?:[^\\"]|\\\\.)* to perform exponential time matching, consuming CPU resources for the worker thread. An attacker can send such a header without authentication, making each request take over 30 seconds of CPU time. Repeated requests can saturate all worker threads, effectively shutting down the Swift proxy and denying service to legitimate users.

Affected Systems

The flaw exists in OpenStack Swift releases through 2.38.0. Any deployment of the Swift proxy component in those versions is vulnerable; this includes installations in public clouds, private clouds, and hybrid environments that rely on the OpenStack Swift object storage service.

Risk and Exploitability

The CVSS score of 8.7 reflects a high‑severity denial‑of‑service condition. EPSS data is currently unavailable, and the vulnerability is not in the CISA KEV catalog. The attack vector is remote, unauthenticated, and exploits the regular expression parser. By sending crafted Accept headers, an attacker can exhaust CPU cycles and worker threads, leading to a complete denial of service.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

OpenStack

Swift

unaffected

Version	Status	Constraints
`1.9.1`	affected	< 2.35.4
`2.36.0`	affected	< 2.36.3
`2.37.0`	affected	< 2.37.3
`2.38.0`	affected	—

No data.

Vendor Product Confidence Versions

Openstack

Swift

95%

Version	Status	Scheme	Platform
`[1.9.1,2.35.4)`	affected	semver	—
`[2.36.0,2.36.3)`	affected	semver	—
`[2.37.0,2.37.3)`	affected	semver	—
`2.38.0`	affected	semver	—

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Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

Update to the latest OpenStack Swift release that patches the Accept header parsing regex (e.g., 2.38.x or newer).
If upgrading is delayed, apply application‑level rate limiting or firewall rules to restrict the frequency of requests to the Swift proxy, reducing the impact of ReDoS attempts.
Monitor Swift worker CPU usage and set alerts for abnormal CPU spikes to detect ongoing ReDoS attacks early.

Generated by OpenCVE AI on August 5, 2026 at 06:53 UTC.

Tracking

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Advisories

Source	ID	Title
Debian DLA	DLA-4746-1	swift security update

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00538.

Exploitation none

Automatable yes

Technical Impact partial

References

Link	Providers
http://www.openwall.com/lists/oss-security/2026/08/05/19
https://launchpad.net/bugs/2158771
https://nvd.nist.gov/vuln/detail/CVE-2026-71190
https://openwall.com/lists/oss-security/2026/07/28/27
https://security.openstack.org/ossa/OSSA-2026-031.html
https://www.cve.org/CVERecord?id=CVE-2026-71190

History

Thu, 06 Aug 2026 14:30:00 +0000

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Thu, 06 Aug 2026 12:15:00 +0000

Type	Values Removed	Values Added
Title	OpenStack Swift Accept Header Regular Expression ReDoS Enables Denial of Service	openstack-swift: openstack-swift: Unauthenticated denial of service via catastrophic backtracking in Accept header parser
References		https://nvd.nist.gov/vuln/detail/CVE-2026-71190 https://www.cve.org/CVERecord?id=CVE-2026-71190
Metrics	threat_severity `None`	cvssV3_1 `{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}` threat_severity `Moderate`

Wed, 05 Aug 2026 07:15:00 +0000

Type	Values Removed	Values Added
Title		OpenStack Swift Accept Header Regular Expression ReDoS Enables Denial of Service

Wed, 05 Aug 2026 05:30:00 +0000

Type	Values Removed	Values Added
Description		In OpenStack Swift through 2.38.0, the proxy server Accept header parser contains a regular expression vulnerable to catastrophic backtracking (ReDoS). The "qdtext" pattern (?:[^"]\|\\.)* allows an unauthenticated remote attacker to send a crafted Accept header that causes exponential CPU consumption in the proxy worker. A payload of 32 backslash-character pairs exceeds 30 seconds of CPU time. No authentication is required. Repeated requests can exhaust all proxy worker threads, resulting in a complete denial of service.
First Time appeared		Openstack Openstack swift
Weaknesses		CWE-1333
CPEs		cpe:2.3:a:openstack:swift::::::::
Vendors & Products		Openstack Openstack swift
References		https://launchpad.net/bugs/2158771 https://openwall.com/lists/oss-security/2026/07/28/27 https://security.openstack.org/ossa/OSSA-2026-031.html
Metrics		cvssV4_0 `{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}`

Subscriptions

Openstack Swift

MITRE

Status: PUBLISHED

Assigner: mitre

Published: 2026-08-05T04:54:03.020Z

Updated: 2026-08-06T13:09:17.168Z

Reserved: 2026-08-05T04:54:02.394Z

Link: CVE-2026-71190

Vulnrichment

Updated: 2026-08-05T18:32:08.027Z

NVD

Status : Received

Published: 2026-08-05T06:16:40.023

Modified: 2026-08-06T14:16:41.060

Link: CVE-2026-71190

Redhat

Severity : Moderate

Publid Date: 2026-07-28T15:00:00Z

Links: CVE-2026-71190 - Bugzilla

OpenCVE Enrichment

Updated: 2026-08-05T07:00:10Z

Weaknesses

CWE-1333
Inefficient Regular Expression Complexity

Impact

Affected Systems

Risk and Exploitability

Tracking

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

Exploitation none

Automatable yes

Technical Impact partial

Subscriptions

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