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CVE-2026-77640 Details

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.

Metrics

CVSS 3.x Severity and Vector Strings:

NIST: [email protected]CVSS-B:5.3 MEDIUMVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CNA: [email protected]CVSS-B:3.7 LOWVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLog	[email protected]	Permissions RequiredRelease NotesVendor Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-1284	Improper Validation of Specified Quantity in Input	[email protected]

Affected Products

Product	Versions
torproject tor	< 0.4.9.9
CPE cpe:2.3:a:torproject:tor:::::::: Remediation No remediation found in references.

Change History

3 change records found show changes

Date	Action	Recorded By
Sep 8, 2026	Initial Analysis	[email protected]
Aug 21, 2026	CVE Modified	CISA-ADP
Aug 20, 2026	New CVE Received	[email protected]