CVE-2026-77639: tor before 0.4.9.9 (exclusive); +1 more affected products

Affected technology

tor · before 0.4.9.9 (exclusive)
torproject

Tor · 0.3.1.1-alpha to before 0.4.9.9
torproject

Description’s affected range: before 0.4.9.9 was prone to a compression bomb bypass where an attacker could concatenate many gzip or zlib sub-streams

Component: Not specified by the source

Attack conditions (Vendor/CNA, CVSS 3.1): Network (remote) · No privileges required · No user interaction required

What an attacker can do

A compression bomb bypass where an attacker could concatenate many gzip or zlib sub-streams, each just under the per-stream detection threshold, to avoid the compression bomb check entirely. Vendor/CNA’s CVSS 3.1 assessment (base score 5.3/10) rates confidentiality and integrity impact as none; availability impact as low.