CVE-2026-31924: Apache APISIX Information Disclosure Flaw

CVE-2026-31924 Overview

CVE-2026-31924 is a Cleartext Transmission of Sensitive Information vulnerability affecting Apache APISIX, a popular open-source API gateway. The vulnerability exists in the tencent-cloud-cls log export functionality, which transmits log data using plaintext HTTP instead of encrypted HTTPS connections. This security flaw could allow network-positioned attackers to intercept sensitive information contained in log exports through man-in-the-middle attacks or passive network sniffing.

Critical Impact

Sensitive log data transmitted via the tencent-cloud-cls integration may be intercepted by attackers with network access, potentially exposing API keys, user credentials, request parameters, and other confidential information logged by the API gateway.

Affected Products

• Apache APISIX versions 2.99.0 through 3.15.0
• Deployments using the tencent-cloud-cls log export feature
• Environments where APISIX log exports traverse untrusted networks

Discovery Timeline

• April 14, 2026 - CVE-2026-31924 published to NVD
• April 14, 2026 - Last updated in NVD database

Technical Details for CVE-2026-31924

Vulnerability Analysis

This vulnerability is classified under CWE-319 (Cleartext Transmission of Sensitive Information). The root issue lies in the tencent-cloud-cls log export plugin's network communication implementation, which defaults to or exclusively uses unencrypted HTTP protocol when transmitting log data to Tencent Cloud Log Service (CLS) endpoints.

In API gateway deployments, logs typically contain highly sensitive information including HTTP headers (which may contain authentication tokens), request/response bodies, client IP addresses, user identifiers, and backend service details. When this data is transmitted over plaintext HTTP, any entity with access to the network path—including malicious actors performing ARP spoofing, compromised network equipment, or adversaries on shared network segments—can capture and read the transmitted logs.

The vulnerability has a network-based attack vector, requiring no authentication or user interaction. While the confidentiality impact is limited to the log data being transmitted, this data often contains credentials and sensitive business information that could be leveraged for further attacks.

Root Cause

The underlying cause of this vulnerability is the use of plaintext HTTP protocol in the tencent-cloud-cls log export plugin rather than HTTPS with proper TLS encryption. This represents an insecure default configuration or missing encryption enforcement in the plugin's HTTP client implementation. Proper transport layer security was not implemented or enforced for outbound log transmissions, violating security best practices for handling sensitive data in transit.

Attack Vector

An attacker positioned on the network path between the Apache APISIX instance and the Tencent Cloud CLS endpoint can intercept log data. Attack scenarios include:

The attacker could perform passive network monitoring on shared network segments, capturing all unencrypted HTTP traffic. In more active attack scenarios, an adversary could execute ARP spoofing or DNS hijacking to redirect traffic through their controlled system. In cloud environments, compromised neighboring instances on shared infrastructure could potentially sniff network traffic.

The vulnerability can be exploited by monitoring HTTP traffic on port 80 destined for Tencent Cloud CLS endpoints. Log data containing sensitive API request/response information would be visible in plaintext within the captured network packets. See the Apache mailing list discussion for additional technical context.

Detection Methods for CVE-2026-31924

Indicators of Compromise

• Outbound HTTP (non-HTTPS) connections from APISIX instances to Tencent Cloud CLS endpoints
• Network traffic analysis showing unencrypted log data in transit on port 80
• Unexpected queries or access patterns indicating leaked credential usage

Detection Strategies

• Monitor network traffic for plaintext HTTP connections originating from APISIX servers to external log collection services
• Review APISIX plugin configurations for the tencent-cloud-cls plugin and verify protocol settings
• Implement network-based intrusion detection rules to alert on sensitive data patterns in unencrypted traffic

Monitoring Recommendations

• Deploy network traffic analysis tools to identify cleartext transmissions containing sensitive patterns
• Enable APISIX access logging to track plugin configuration changes
• Implement egress filtering to block or alert on plaintext HTTP connections to known cloud service endpoints

How to Mitigate CVE-2026-31924

Immediate Actions Required

• Upgrade Apache APISIX to version 3.16.0 or later, which addresses this vulnerability
• Audit current tencent-cloud-cls plugin configurations for HTTP vs HTTPS usage
• Temporarily disable the tencent-cloud-cls log export feature if immediate upgrade is not possible
• Review logs for any signs of sensitive data exposure during the vulnerable period

Patch Information

Apache has released version 3.16.0 of APISIX which fixes this cleartext transmission issue. Users running versions 2.99.0 through 3.15.0 should upgrade immediately. The fix ensures that log exports to Tencent Cloud CLS use encrypted HTTPS connections. For detailed information, refer to the Apache mailing list announcement and the OpenWall security discussion.

Workarounds

• Disable the tencent-cloud-cls log export plugin until the upgrade can be applied
• If the plugin must remain active, ensure network-level encryption (VPN/IPsec) is in place between APISIX and the CLS endpoint
• Implement network segmentation to limit exposure of the traffic path
• Consider using alternative log export methods that support HTTPS until the patch is applied

# Configuration example - Disable tencent-cloud-cls plugin until patched
# In APISIX configuration (config.yaml), ensure the plugin is not loaded:
plugins:
  - ... # other plugins
  # - tencent-cloud-cls  # Comment out or remove this line

# After upgrading to 3.16.0+, re-enable with HTTPS enforcement
# Verify APISIX version after upgrade:
apisix version