CVE-2026-77640
tor before 0.4.9.9 was prone to an infinite loop when decompressing a truncated zlib/gzip stream with done=1.
Does this matter?
Lower severity and a low EPSS score (0.38%). Track it; it rarely justifies an emergency change on its own.
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.
- 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
- 0.38% probability · 32th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-1284
- Affected
- torproject/tor
- Source
- cve@mitre.org
EPSS 0.4% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLogPermissions Required, Release Notes, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.