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CVE Record

CVE-2021-34549: An issue was discovered in Tor before 0.4.6.5, aka TROVE-2021-005.

An issue was discovered in Tor before 0.4.6.5, aka TROVE-2021-005. Hashing is mishandled for certain retrieval of circuit data. Consequently. an attacker can trigger the use of an attacker-chosen circuit ID to cause algorithm inefficiency.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-34549 affects Tor versions before 0.4.6.5. The issue lets an attacker influence circuit ID handling in a way that causes inefficient processing. The sources point to availability and performance risk rather than data theft or code execution. No source in the bundle shows active exploitation.

Executive priority

Address during normal vulnerability remediation, faster for exposed Tor infrastructure or business-critical services. The issue appears availability-focused and lacks evidence of active exploitation, but unpatched Tor nodes before 0.4.6.5 remain needlessly exposed.

Technical view

Tor mishandles hashing during certain circuit data retrieval, allowing attacker-chosen circuit IDs to trigger algorithmic inefficiency. The CVE identifies the issue as TROVE-2021-005 and states Tor before 0.4.6.5 is affected. The bundle does not provide CVSS, CWE mapping, exploit detail, or a complete affected platform matrix.

Likely exposure

Exposure is limited to systems running Tor before 0.4.6.5. Internet-reachable Tor relays, clients, or services using vulnerable Tor builds may be more exposed, but the bundle does not identify specific deployments, packages, or configurations beyond the Tor version boundary.

Exploitation context

The CVE describes attacker-triggered inefficiency through circuit ID handling. It does not document public exploit code, real-world exploitation, or inclusion in CISA KEV. Treat this as a plausible denial-of-service or resource-consumption risk, with exploitation status unconfirmed by the provided sources.

Researcher notes

The source bundle is sparse: no CVSS, CWE, detailed patch analysis, or exploit telemetry is included. Anchor assessment to the stated version boundary and Tor’s TROVE-2021-005 identifier. Avoid assuming impact beyond algorithmic inefficiency unless vendor sources provide more detail.

Mitigation direction

  • Upgrade Tor to version 0.4.6.5 or later.
  • Apply vendor or distribution security updates, including Gentoo GLSA-202107-25 where relevant.
  • Check Tor Project guidance for any version-specific remediation notes.
  • Prioritize exposed relays or Tor-dependent production services.

Validation and detection

  • Inventory all systems running Tor and record exact versions.
  • Confirm deployed Tor versions are 0.4.6.5 or later.
  • Verify distribution security advisories have been applied on managed hosts.
  • Review monitoring for unexplained Tor CPU or latency spikes.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2021-34549 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
4Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.