Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessSend crafted HTTP request with embedded regex token
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DeliveryATS evaluates unanchored pattern as substring match
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ExploitATS incorrectly grants policy compliance
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ExecutionRequest forwarded to protected upstream resource
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ImpactConfidential response returned to attacker
Vulnerability Assessment
| Weakness |
CWE
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| Exploitation Conditions | Exploitation requires that the target Apache Traffic Server instance uses one or more regular expression rules - in remap.config, ACL plugins, or header-rewriting configurations - where the pattern is applied to request URIs, hostnames, or headers for a security enforcement decision and lacks proper anchoring. Default ATS configurations with no regex-based access control are not vulnerable to the authorization bypass; the flaw only materializes when regex rules are actively used as security gatekeepers. No authentication is required (PR:N), no user interaction is needed (UI:N), and attack complexity is low (AC:L) once the regex pattern structure is known or guessed. Exploitation is limited to confidentiality breach (C:H) and minor integrity bypass (I:L); availability is not impacted. |
| Impact | The CVSS 3.1 base score of 8.2 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N) accurately reflects a remotely exploitable, low-complexity, unauthenticated path to high confidentiality impact. The attack vector is purely network-based with no privileges or user interaction required, making this accessible to any actor capable of sending HTTP requests. The I:L metric suggests limited but non-zero write-path bypass - for example, permitting a write to a path that should be read-only under the regex policy. No EPSS score was provided in the input data; given that no POC and no KEV listing exist at time of analysis, real-world exploitation probability is lower than the CVSS score alone suggests, but the simplicity of the attack class (substring embedding in a request) means weaponization would be trivial once an attacker identifies the specific unanchored pattern in use. The actual risk is highly deployment-dependent: installations using ATS regex rules for security enforcement (access control, content gating) are materially exposed, while installations relying on network-layer ACLs or not using regex-driven policies face limited exposure from this specific flaw. |
| Exploit ScenarioDerived | An attacker targeting an ATS deployment that uses an unanchored regex such as /^secret/ to gate access to a protected upstream path sends a crafted HTTP request for a URI like /public/secret/data - because the pattern matches the substring 'secret' without anchoring at the right position, ATS evaluates the request as policy-compliant and forwards it to the protected upstream, returning confidential content to the unauthenticated attacker. No public exploit code exists at time of analysis, but the technique requires only knowledge of the target regex pattern and the ability to embed it as a substring in a crafted request path or header. |
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Alert meAnalysisAIv1 – Jul 29, 2026
Unanchored regular expression matching in Apache Traffic Server exposes a high-severity bypass that allows remote unauthenticated attackers to circumvent regex-based access controls, potentially leaking protected content (C:H) and enabling limited unauthorized writes (I:L). All 9.0.x through 9.2.14 and 10.0.x through 10.1.3 deployments that rely on regex-driven rules for routing, ACL, or header policy enforcement are at risk. No public exploit code has been identified at time of analysis, and CISA has not listed this in KEV, but the low-complexity, unauthenticated network attack path makes it a realistic opportunistic target for any actor aware of the flaw.
RemediationAI
Upgrade to Apache Traffic Server 9.2.15 (for the 9.x line) or 10.1.4 (for the 10.x line), both confirmed as patched releases per the vendor advisory at https://lists.apache.org/thread/5prl9glcm9g2swnq9hqxvnokylm1gr6d. If immediate upgrade is not feasible, audit all regex patterns configured in remap.config, parent.config, and plugin configurations to manually add ^ and $ anchors to any pattern used for security-enforcement decisions - this directly addresses the root CWE-777 condition, though operator-applied fixes carry risk of misconfiguration and do not replace the vendor patch. As a compensating control, place ATS behind a WAF or upstream proxy that independently enforces URI and header allow-listing, reducing reliance on ATS-internal regex ACLs; note this adds latency and operational complexity. Avoid relying on regex-based access control in ATS as the sole enforcement layer until patched.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in euvd
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Technical ContextAI · show details
Apache Traffic Server (ATS) is a high-performance reverse proxy and HTTP caching layer used in large-scale CDN and load-balancing infrastructures (CPE: cpe:2.3:a:apache_software_foundation:apache_traffic_server). The root cause is CWE-777 - Regular Expression without Anchors - where a security-relevant regex pattern lacks start (^) or end ($) anchors. Without anchors, a pattern intended to match only a specific URI path, hostname, or header value will also match any string that contains the target pattern as a substring. In ATS, such regex rules govern ACL decisions, plugin behavior, or header rewriting. An attacker can craft a request whose path or header embeds the expected token as a substring while containing additional untrusted content, causing ATS to incorrectly treat the request as matching the intended policy and granting it elevated access or forwarding it to protected upstream resources.
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Severity by source
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N
Network-reachable proxy, no auth or interaction needed; high confidentiality loss from access control bypass, limited integrity, no availability impact.
Primary rating from Vendor (apache).
CVSS VectorVendor: apache
Lifecycle Timeline
2DescriptionCVE.org
Regular Expression without Anchors vulnerability in Apache Traffic Server.
This issue affects Apache Traffic Server: from 10.0.X through 10.1.3, from 9.0.X through 9.2.14.
Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fixes the issue.
Threat Intelligence Overview
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.
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EUVD-2026-50168
GHSA-mhwr-5c6p-qj97
NVD
CVE.org
EPSS
Vulnrichment
VulDB
Exploit-DB