CVE-2026-77640
Low
Description
tor before 0.4.9.9 was prone to an infinite loop when decompressing a truncated zlib/gzip stream with done=1. A truncated stream never reaches Z_STREAM_END, causing zlib to return Z_BUF_ERROR with no input remaining, which buf_add_compress() mistook for a full output buffer and retried forever. Fixed by returning TOR_COMPRESS_ERROR in that case so the caller can abort cleanly. This is TROVE-2026-021.
SeverityLow
CVSS3.7
Exploit probability—
ProductTor
PublishedAug 20, 2026
First seenAug 20, 2026
Weakness typeCWE-1284CWE-1284
How to fix
Update
- torproject tor0.4.9.9 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| torproject tor | v < 0.4.9.9 | 0.4.9.9 |
Check your version
Choose the product and enter the version you run to see whether it falls in the affected range.
In the Intelligence 360 plan
Attack Surface Management
See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.