CVE-2026-77584

Received Received - Intake

Tor 0.4.9.10 Use-After-Free in CONFLUX_LINK Handling

Publication date: 2026-08-20

Last updated on: 2026-08-20

Assigner: MITRE

Description

Tor before 0.4.9.10 did not reject a CONFLUX_LINK cell that arrives on a circuit which already has attached streams. A malicious client could send a RELAY_COMMAND_BEGIN before the CONFLUX_LINK on the same circuit, attaching an exit stream that would later end up orphan leaving a dangling circuit back-pointer and a use-after-free (UAF) when the circuit is freed. This is TROVE-2026-025.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-08-20

Last Modified

2026-08-20

Generated

2026-08-21

AI Q&A

2026-08-21

EPSS Evaluated

N/A

NVD

CVE-2026-77584

EUVD

EUVD-2026-63591

Affected Vendors & Products

Vendor	Product	Version / Range
tor_project	tor	to 0.4.9.10 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-821	The product utilizes a shared resource in a concurrent manner, but it does not correctly synchronize access to the resource.

Attack-Flow Graph

Executive Summary

This vulnerability involves a flaw in Tor before version 0.4.9.10 where a CONFLUX_LINK cell is not properly rejected if it arrives on a circuit already handling streams. A malicious client could exploit this by sending a RELAY_COMMAND_BEGIN before the CONFLUX_LINK, creating a dangling circuit back-pointer and leading to a use-after-free (UAF) when the circuit is freed.

Impact Analysis

An attacker could exploit this to cause a crash or execute arbitrary code on systems running vulnerable Tor versions. This may lead to denial-of-service conditions or potential compromise of anonymity and privacy for users relying on Tor for secure communication.

Mitigation Strategies

Upgrade Tor to version 0.4.9.10 or later to address the vulnerability. Ensure all Tor clients and relays are updated to prevent exploitation.

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