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CVE-2021-3449 is a denial-of-service vulnerability in OpenSSL 1.1.1 affecting TLS server-side processing of TLSv1.2 renegotiation. A malicious client can trigger a NULL pointer dereference by sending a crafted renegotiation ClientHello in which the initial handshake included the signature_algorithms extension, but the renegotiation ClientHello omits signature_algorithms while including signature_algorithms_cert. This inconsistent extension state causes OpenSSL to dereference a NULL pointer during signature_algorithms processing, crashing the server process. The issue affects OpenSSL TLS servers in the 1.1.1 through 1.1.1j range. OpenSSL clients are not affected, and OpenSSL 1.0.2 is not impacted.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository provides a proof-of-concept (PoC) exploit for CVE-2021-3449, a denial-of-service vulnerability in OpenSSL versions prior to 1.1.1k. The exploit is implemented in Go and works by connecting to a TLS server and performing a malicious renegotiation handshake, which triggers a NULL pointer dereference in the server's OpenSSL library, causing it to crash. The main exploit logic is in `main.go` and the custom TLS logic is in the `tls/` directory, which is a modified copy of Go's standard library TLS implementation to allow for the crafted handshake. The repository also includes a comprehensive `demo/` directory with Dockerfiles and configurations for various popular server applications (OpenSSL s_server, Apache, HAProxy, lighttpd, nginx, Node.js) to demonstrate the exploit against real targets using the vulnerable OpenSSL version. The Makefile automates building the exploit and running it against these demo targets. The exploit is network-based and targets any TLS server using a vulnerable OpenSSL version with TLSv1.2 and secure renegotiation enabled. No fake or destructive payloads are present; the exploit is a legitimate denial-of-service PoC.
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6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An OpenSSL vulnerability mentioned only in related content, not part of the main article.
A denial of service vulnerability observed being targeted against the Stockholm honeypot.
A high-severity OpenSSL denial-of-service vulnerability in TLSv1.2 renegotiation handling that can crash vulnerable TLS servers via a maliciously crafted ClientHello message.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.