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The CVE-2025-53017 vulnerability is triggered when the Versity Gateway (using the fasthttp library) processes an AWS S3 chunked upload request that lacks a standard HTTP Content-Length header. Internally, fasthttp assigns a special value of -2 to the ContentLength field when this header is absent. This value causes the ContinueReadBodyStream function to exit prematurely without initializing a body reader (io.Reader) in the request context. However, Versity’s checksum calculation routine in HashReader unconditionally attempts to use this non-existent reader, leading to a null pointer dereference and a immediate process panic, crashing the server. This specific request structure is forced when the AWS CLI v2 communicates through an SSL-terminating nginx proxy, which alters the upload strategy to use chunked encoding.
Platform: Versity Gateway
Version: (pre-patch versions)
Vulnerability: Null Pointer Dereference
Severity: Critical
date: 2025-07-18
Prediction: 2025-08-15
What Undercode Say:
aws s3 cp largefile.txt s3://bucket/ --endpoint-url https://proxy:7070
// csum-reader.go - HashReader function snippet
func (c HashReader) Read(p []byte) (n int, err error) {
n, err = c.r.Read(p) // Panic occurs here, c.r is nil
// fasthttp/headers.go - parseHeaders function h.contentLength = -2 // Initial value, replaced if header exists
How Exploit:
Crafted AWS chunked request without Content-Length header.
Protection from this CVE:
Patch fasthttp integration.
Impact:
Remote Denial-of-Service (Crash).
🎯Let’s Practice Exploiting & Learn Patching For Free:
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
