CVE-2026-77640

published 2026-08-20

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. A truncated stream never reaches Z_STREAM_END…

Priority P4 27 medium 5.3 CVSS 3.1

AV N AC L PR N UI N S U C N I N A L

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.

Affected

2 ranges

Vendor	Product	Version range	Fixed in
torproject	tor	< 0.4.9.9	0.4.9.9
torproject	tor	>= 0.2.6.1-alpha < 0.4.9.9	0.4.9.9

Stop checking back — get the weekly exploitation signal.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.

CWE-1284