VulnerabilityAnalyzed
CVE-2026-77639
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.
MEDIUM 5.3EPSS 0.23%
Does this matter?
Lower severity and a low EPSS score (0.23%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 5.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- EPSS
- 0.23% probability · 14th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-420
- Affected
- torproject/tor
- Source
- cve@mitre.org
References
- https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLogRelease Notes, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.