CVE-2026-44597Network attack vector

Service interruption via missing cell reason validation

Published May 7, 2026 · Updated May 7, 2026

Out-of-bounds read in Tor before 0.4.9.7 allows remote attackers to interrupt service via malformed circuit-closing cells. The circuit-cell handlers read a reason octet from an END, TRUNCATE, or TRUNCATED payload without first requiring that the octet exists. An unauthenticated network peer must supply one of those cells without a reason, producing an availability-only service interrupt.

CVSS severity3.7
Low
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in Tor before 0.4.9.7 allows remote attackers to interrupt service via malformed circuit-closing cells. The circuit-cell handlers read a reason octet from an END, TRUNCATE, or TRUNCATED payload without first requiring that the octet exists. An unauthenticated network peer must supply one of those cells without a reason, producing an availability-only service interrupt.

The record

CVE
CVE-2026-44597
Published
May 7, 2026
Updated
May 7, 2026
Vendor
The Tor Project
Product
Tor
Classifications
CWE-684, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 7, 2026CVE publishedPublication date reported by the CVE source.
  2. May 7, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <0.4.9.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Tor Project · Torversion=0 <0.4.9.7

Published CVSS scores

3.7MITRECVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-684Incorrect Provision of Specified Functionality
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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