# CVE-2026-77639

## Summary

- **CVE ID:** CVE-2026-77639
- **Severity:** MEDIUM
- **CVSS Score:** 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)
- **CWE:** CWE-420
- **Published:** Aug 20, 2026
- **Last Modified:** Aug 21, 2026

## 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.

## Affected Products

- torproject — Tor (0.3.1.1-alpha)

## References

- [CNA](https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLog)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.23%
- **EPSS Percentile:** 13.9

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._