A 100-line exploit rickrolled the NSA 24 hours after Microsoft patched CryptoAPI

Less than 24 hours after Microsoft disclosed CVE-2020-0601 — the critical Windows CryptoAPI flaw Microsoft patched on January 14, 2020 after a private tipoff from the NSA — researcher Saleem Rashid tweeted images of Rick Astley's 'Never Gonna Give You Up' playing on GitHub.com and NSA.gov over HTTPS. The rickroll was the demonstration: his exploit made Edge and Chrome treat spoofed sites as genuinely verified, with Brave, other Chrome derivatives and Internet Explorer likely affected too. Firefox showed no indication of being affected.

The flaw completely broke certificate validation for websites, software updates, VPNs and other security-critical uses on Windows 10, including Windows Server 2016 and 2019. The mechanics: CryptoAPI trusted elliptic-curve parameters included with each certificate rather than requiring standards-defined curves, so an attacker could supply custom generator parameters — letting Windows 'agree' on a public key the attacker had chosen, and making forged certificates pass as real.

Rashid said the exploit used about 100 lines of code, and that he could compress it to 10 if he dropped 'a few useful tricks.' The speed of the demonstration — inside a day, against a flaw disclosed without a public technical description — showed how little gap remained between 'patched vulnerability' and 'weaponized exploit' when the root cause is a design error rather than a memory bug.

The disclosure's origin gave the story its irony: the NSA had privately reported the bug, whose practical effect included impersonating the NSA's own website. Rickrolling — the standard humorous demonstration of serious security flaws — made the impersonation visible to non-experts immediately.

The root cause is a design principle, not an implementation slip: accepting caller-supplied cryptographic parameters converts agility into universal forgery.

The impact radius was everything TLS protects — websites, software updates, VPNs — across all Windows 10 and Server 2016/2019 machines.

A working spoof landed in about 100 lines within a day of disclosure, before most defenders had even applied the patch.

The demonstration target was the reporter of the bug itself, making the failure mode impossible to dismiss as theoretical.

Cryptographic agility is attack surface: every parameter a verifier will accept from the untrusted side is a knob the attacker can turn — hard-code the constants, verify nothing optional.

Microsoft's January 14, 2020 patch fixed the CryptoAPI validation flaw for Windows 10 and the affected server versions; the source reports no in-the-wild exploitation beyond Rashid's demonstration.