CVE-2026-13762 Overview
CVE-2026-13762 is an HTTP request smuggling vulnerability affecting Amazon CloudFront distributions with AWS WAF enabled. Remote attackers can craft HTTP/2 requests that fragment the request body across multiple frames. This inconsistent interpretation causes AWS WAF managed rules to inspect only a partial body, bypassing body inspection controls. The flaw is classified under [CWE-444] (Inconsistent Interpretation of HTTP Requests). Amazon remediated the issue server-side, and no customer action is required. The vulnerability was disclosed in AWS Security Bulletin #2026-048.
Critical Impact
Attackers can bypass AWS WAF managed rule body inspection by fragmenting HTTP/2 request bodies, allowing malicious payloads to reach origin applications undetected.
Affected Products
- Amazon CloudFront distributions with AWS WAF enabled
- AWS WAF managed rule groups performing HTTP request body inspection
- Origin applications protected behind CloudFront + AWS WAF
Discovery Timeline
- 2026-06-29 - CVE-2026-13762 published to NVD
- 2026-07-01 - Last updated in NVD database
- 2026-07-02 - EPSS scoring published (0.438%)
Technical Details for CVE-2026-13762
Vulnerability Analysis
The vulnerability stems from inconsistent HTTP/2 request handling between AWS WAF's inspection layer and CloudFront's forwarding logic. HTTP/2 permits request bodies to be split across multiple DATA frames. Attackers craft requests where the body is fragmented in a way that AWS WAF only parses the initial frame, while CloudFront reassembles the full body and forwards it to the origin.
AWS WAF managed rules rely on body inspection to identify SQL injection, cross-site scripting, and other payload-based attacks. When only a partial body is inspected, malicious content in subsequent frames evades identification. The origin receives the complete, malicious request as if no WAF were present.
Root Cause
The root cause is a parser differential between the WAF inspection component and the CloudFront proxy component. Both components handle HTTP/2 framing, but they apply different logic when reconstructing request bodies from multi-frame streams. This desynchronization allows crafted DATA frame sequences to be interpreted differently by each component.
Attack Vector
Exploitation requires network access to a CloudFront endpoint fronting a WAF-protected origin. The attacker constructs an HTTP/2 request that fragments the body such that WAF inspection terminates before the malicious payload is reached. No authentication or user interaction is required. The AWS Security Bulletin confirms this issue was remediated server-side across the CloudFront fleet.
Exploitation code is not publicly available, and the AWS advisory does not disclose crafted-frame specifics. Refer to the AWS Security Bulletin #2026-048 for authoritative remediation details.
Detection Methods for CVE-2026-13762
Indicators of Compromise
- HTTP/2 requests to CloudFront distributions containing unusually fragmented DATA frame sequences
- Origin application logs showing malicious payloads (SQLi, XSS, command injection) that were not flagged by AWS WAF
- Discrepancies between AWS WAF sampled request bodies and origin-received request bodies
Detection Strategies
- Correlate AWS WAF logs with origin application logs to identify requests where inspected body content differs from received body content
- Alert on origin-side detections of attack payloads that traversed WAF-protected paths without a corresponding WAF match
- Baseline HTTP/2 frame counts per request and flag statistical outliers with high DATA frame fragmentation
Monitoring Recommendations
- Enable AWS WAF full request logging to CloudWatch Logs or S3 for retrospective analysis
- Forward CloudFront access logs and origin application logs into a centralized analytics platform for cross-layer correlation
- Monitor AWS security bulletins for follow-up advisories related to HTTP/2 handling in CloudFront and AWS WAF
How to Mitigate CVE-2026-13762
Immediate Actions Required
- No customer action is required. AWS remediated the vulnerability server-side across the CloudFront service
- Review AWS WAF and CloudFront logs from before the remediation date for signs of exploitation attempts against protected origins
- Validate that origin applications enforce defense-in-depth input validation, independent of WAF inspection
Patch Information
Amazon deployed the fix at the service layer. Customers using Amazon CloudFront with AWS WAF automatically receive the corrected HTTP/2 request handling behavior. See AWS Security Bulletin #2026-048 for the official advisory.
Workarounds
- Implement origin-side input validation and payload inspection so that WAF bypass alone is insufficient to compromise the application
- Deploy AWS WAF rate-based rules and IP reputation rules to constrain volumetric abuse independent of body inspection
- Consider enforcing HTTP/1.1 on sensitive endpoints during incident response if a similar parser differential is suspected in the future
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
