VulnerabilityPublished 18 Sep 2026Updated 17 Oct 2026

CVE-2026-89058: RESTEasy's CorsFilter, which · CWE-346

Affects resteasySource GCVE Database

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Authoritative record:CVE-2026-89058· High 7.4

Not known to be exploited · CVSS 7.4 High.

Data as of 7 Nov 2026, 23:24 UTC

CVSS 3.1 base score

7.4High

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (redhat)	CVSS 3.1	7.4

EPSS: 0.4% chance of exploitation in 30 days – higher than 41% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Changed
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 8 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.10resteasy`pkg:deb/ubuntu/resteasy?arch=source&distro=stonking`Other threats	Affected =3.6.2-4	Fixed in–
Ubuntu 26.10resteasy3.0`pkg:deb/ubuntu/resteasy3.0?arch=source&distro=stonking`Other threats	Affected =3.0.26-6	Fixed in–
Ubuntu 26.04 LTSresteasy`pkg:deb/ubuntu/resteasy?arch=source&distro=resolute`Other threats	Affected =3.6.2-3 =3.6.2-4	Fixed in–
Ubuntu 26.04 LTSresteasy3.0`pkg:deb/ubuntu/resteasy3.0?arch=source&distro=resolute`Other threats	Affected =3.0.26-6	Fixed in–
Ubuntu 24.04 LTSresteasy3.0`pkg:deb/ubuntu/resteasy3.0?arch=source&distro=noble`Other threats	Affected =3.0.26-6 =3.0.26-6ubuntu0.24.04.1	Fixed in–
Ubuntu Pro 24.04 LTSresteasy`pkg:deb/ubuntu/resteasy?arch=source&distro=esm-apps/noble`Other threats	Affected =3.6.2-2 =3.6.2-2ubuntu0.24.04.1~esm1	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Until an official fix is available, avoid configuring RESTEasy's CorsFilter to allow all origins ('*') with Access-Control-Allow-Credentials set to true. Restrict CORS policies to specific trusted origins to prevent credentialed cross-origin requests from untrusted sources.

Description

CVE-2026-89058 is a vulnerability in RESTEasy's CorsFilter that occurs when it is configured to allow all origins ('*'). The flaw causes the server to reflect the request's Origin header back in the Access-Control-Allow-Origin response and sets Access-Control-Allow-Credentials to true. This misconfiguration allows malicious websites to perform credentialed cross-origin requests and read authenticated responses from a victim's session, resulting in loss of confidentiality.

Impact

An attacker controlling a malicious website can exploit this vulnerability to perform credentialed cross-origin requests to a vulnerable RESTEasy service. Because the Access-Control-Allow-Origin header reflects the Origin header and Access-Control-Allow-Credentials is true, the attacker can read sensitive authenticated responses from the victim's session. This leads to a loss of confidentiality of user data accessible via the vulnerable service.

CWE-346Origin Validation Error (opens in a new tab)
Class weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product does not properly verify that the source of data or communication is valid.
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V14.5.2 (opens in a new tab)
V14.5.3 (opens in a new tab)
V1.4.4 (opens in a new tab)
Attack patterns
JSON Hijacking (aka JavaScript Hijacking) (opens in a new tab)
Cache Poisoning (opens in a new tab)
DNS Cache Poisoning (opens in a new tab)
Exploit Script-Based APIs (opens in a new tab)
Application API Message Manipulation via Man-in-the-Middle (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-942Permissive Cross-domain Security Policy with Untrusted Domains (opens in a new tab)
Variant weaknessOWASP Top 10 A02:2025: Security Misconfiguration (opens in a new tab)
The product uses a web-client protection mechanism such as a Content Security Policy (CSP) or cross-domain policy file, but the policy includes untrusted domains with which the web client is allowed to communicate.
Architecture and Design · Operation · Attack Surface Reduction
Define a restrictive Content Security Policy or cross-domain policy file.
Architecture and Design · Operation · Attack Surface Reduction
Avoid using wildcards in the CSP / cross-domain policy file. Any domain matching the wildcard expression will be implicitly trusted, and can perform two-way interaction with the target server.
Architecture and Design · Operation · Environment Hardening
For Flash, modify crossdomain.xml to use meta-policy options such as 'master-only' or 'none' to reduce the possibility of an attacker planting extraneous cross-domain policy files on a server.
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V1.14.1 (opens in a new tab)
V13.4.2 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 18 Oct 2026, 02:14 UTC

WeaknessesCWE-346, CWE-942

Technical details

References

Community reviews

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