Adobe fixed a critical vulnerability in Acrobat and Reader that attackers have been exploiting since at least November 2025. The flaw, CVE-2026-34621, lets hackers execute code simply by getting victims to open a malicious PDF.
Security researcher Haifei Li discovered the exploit on a threat-sharing platform, where it had been sitting largely undetected since March. The sophisticated attack fingerprints victims' systems, steals sensitive data, and can deploy additional malware.
Adobe confirmed active exploitation and released patches on April 11. The company urges immediate updates, as the vulnerability affects the latest versions and requires no user interaction beyond opening the PDF file.
Source: Dark Reading