Tor: Improper Enforcement of a Single, Unique Action
CVE-2026-44601 is a high-severity improper enforcement of a single, unique action vulnerability in Tor from Torproject, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 0.4.9.7 as the first without the flaw, so updating Tor to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.34% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Tor to 0.4.9.7 or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Torproject | Tor | before 0.4.9.7 | 0.4.9.7 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 3.7 | Low | CNA (mitre.org) |
| CVSS 3.1 | 7.5 | High | NVD |
Official description
Tor before 0.4.9.7, when circuit queue memory pressure exists, can experience a client crash because of a double close of a circuit, aka TROVE-2026-009.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Enforcement of a Single, Unique Action
The product requires that an actor should only be able to perform an action once, or to have only one unique action, but the product does not enforce or incorrectly enforces this restriction.
More Improper Enforcement of a Single, Unique Action vulnerabilities (CWE-837)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
- gitlab.torproject.org/tpo/core/tor/-/work_items/41237Not Applicable
Other vulnerabilities in Tor
- 9.3 Critical severity
- 8.2 High severity
- 9.0 Critical severity
- 7.5 High severity
- 8.2 High severity
- 7.5 High severity
Recent Improper Enforcement of a Single, Unique Action vulnerabilities
- 7.5 High severity
Spotted an error? Tell us.