{"id":"CVE-2026-77640","title":"tor before 0.4.9.9 was prone to an infinite loop when decompressing a truncated zlib/gzip  stream with done=1","summary":"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_com…","severity":"low","cvss":3.7,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","cwe":["CWE-1284"],"vendor":"torproject","product":"tor","affected":["tor < 0.4.9.9"],"patched":["tor 0.4.9.9"],"published":"2026-08-20","updated":"2026-09-08","sourceUpdated":"2026-09-08T18:26:07.090","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-77640","references":[{"url":"https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLog","label":"cve@mitre.org"}],"tags":["nvd"],"epss":0.00223,"epssPercentile":0.13207,"ingestedAt":"2026-09-08T19:08:49.591Z","slug":"CVE-2026-77640","body":"## Overview\n\ntor 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.\n\n## Affected\n\n- `tor < 0.4.9.9`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `tor 0.4.9.9`","depth":"sunlit","depthScore":20,"depthScoreParts":{"impact":20.4,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}