CVE-2026-77639: Torproject Tor

Medium severity, CVSS 5.3. EPSS: 0.4% chance of exploitation in the next 30 days.

Tor before 0.4.9.9 was prone to 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. This is TROVE-2026-022.

Affected products

• Torproject Tor: before 0.4.9.9 (fixed in 0.4.9.9)

Published 2026-08-20. Last modified 2026-09-08.