CVE-2026-77639

Compression Bomb Bypass Vulnerability in Tor

Published Aug 20, 2026 CVSS 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Title Compression Bomb Bypass Vulnerability in Tor
Type Values Removed Values Added
Description 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.
First Time appeared Torproject
Torproject tor
Weaknesses CWE-420
CPEs cpe:2.3:a:torproject:tor:*:*:*:*:*:*:*:*
Vendors & Products Torproject
Torproject tor
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
mitre
Published
Updated
Aug 21, 2026, 8:08 PM
Reserved
Aug 20, 2026, 8:57 PM
Status
Analyzed
Published
Aug 20, 2026, 9:17 PM
Modified
Oct 18, 2026, 8:10 PM