Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Attack requirements (AT:N) | No attack requirements |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:N) | No user interaction |
| Confidentiality (VC:H) | High confidentiality impact |
| Integrity (VI:N) | No integrity impact |
| Availability (VA:N) | No availability impact |
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/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
About Istio
CVE-2026-31837 affects Istio, a product from Istio. Before acting, confirm where Istio runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: Istio is an open platform to connect, manage, and secure microservices. Prior to 1.29.1, 1.28.5, and 1.27.8, a user of Istio is impacted if the JWKS resolver becomes unavailable or the fetch fails, exposing hardcoded defaults regardless of use of the RequestAuthentication resource. This vulnerability is fixed in 1.29.1, 1.28.5, and 1.27.8.
The weakness class is Information Exposure. Sensitive information is shown to someone who should not see it.
Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Istio |
| Affected versions | Istio before 1.27.8; Istio from 1.28.0 before 1.28.5; Istio from 1.29.0 before 1.29.1 |
| Published | Mar 10, 2026 |
| Last modified | Jul 20, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | security-advisories@github.com |
How to detect it
- Inventory every instance of Istio and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Istio named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Istio to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-200: Information Exposure More CVEs with this weakness
- CWE-1392 More CVEs with this weakness
Technical References
Frequently asked questions
Related CVEs
The vulnerability exists in BLUVOYIX due to an improper password storage implementation and subsequent exposure via unauthenticated APIs. An unauthenticated remote attacker could exploit this vulnerability by sending specially crafted HTTP requests to the vulnerable users API to retrieve the plaintext passwords of all user users. Successful exploitation of this vulnerability could allow the attacker to gain full access to customers' data and completely compromise the targeted platform by logging in using an exposed admin email address and password.
Exposure of sensitive information to an unauthorized actor in Azure DevOps allows an unauthorized attacker to disclose information over a network.
The vulnerability exists in BLUVOYIX due to the exposure of sensitive internal API documentation. An unauthenticated remote attacker could exploit this vulnerability by sending specially crafted HTTP requests to the APIs exposed by the documentation. Successful exploitation of this vulnerability could allow the attacker to cause damage to the targeted platform by abusing internal functionality.
Other issue in Firefox Focus for Android. This vulnerability was fixed in Firefox 155.
Internally found bugs present in Thunderbird 154. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155 and Thunderbird 155.
Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird ESR 140.14. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Earn your free CTEM certification.
Learn to scope, prioritize, validate and mobilize fixes for CVEs like CVE-2026-31837 with a free CTEM certification.
Beginner / Practitioner / Program Leader
Explore certifications