CVE-2026-77640

EUVD-2026-63650
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.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
mitreCNA
3.7 LOW
NETWORK
HIGH
NONE
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Base Score
CVSS 3.x
EPSS Score
Percentile: Unknown
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
torprojecttor
𝑥
< 0.4.9.9
CNA
Common Weakness Enumeration
References
https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLog