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NVD / CVE Program· CNA mitre

CVE-2021-28090: Tor before 0.4.5.7 allows a remote attacker to cause Tor directory authorities to exit with an assertion failure, aka TROVE-2021-002.

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 2% (FIRST EPSS); higher than 81.6% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: tor (Debian:10) 0.3.5.14-1; tor (Debian:12) 0.4.5.7-1; tor (openSUSE:Leap 15.2) 0.4.5.7-lp152.2.9.1.

Low priority for now. Upgrade to tor (Debian:10) 0.3.5.14-1; tor (Debian:12) 0.4.5.7-1; tor (openSUSE:Leap 15.2) 0.4.5.7-lp152.2.9.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

MediumCVSS 5.3 · v3.1—No exploit Fix available
Published
Mar 19, 2021
Updated
Jun 16, 2026
EPSS
2.0% · 81th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
21 / 40 · 5.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 2.0%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-28090

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
torprojecttor
fedoraprojectfedora

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • fedoraproject fedora33
  • torproject tor0.4.4.4 and later · before 0.4.4.8
  • torproject tor0.4.5.0 and later · before 0.4.5.7
  • torproject torbefore 0.3.5.14
  • torproject tor0.4.4.0
  • torproject tor0.4.4.1
  • torproject tor0.4.4.2
  • torproject tor0.4.4.3

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:10torbefore 0.3.5.14-10.3.5.14-1
Debian:12torbefore 0.4.5.7-10.4.5.7-1
openSUSE:Leap 15.2torbefore 0.4.5.7-lp152.2.9.10.4.5.7-lp152.2.9.1
openSUSE:Tumbleweedtorbefore 0.4.6.7-2.20.4.6.7-2.2
SUSE:Package Hub 15 SP2torbefore 0.4.5.7-bp152.2.9.10.4.5.7-bp152.2.9.1

Same product

torproject: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-77642tor before 0.4.9.9 was prone to an out-of-bounds write when parsing a consensus or detached signature with unexpected signature digest type
    37Monitor
  • CVE-2026-77638Tor before 0.4.9.11 is prone to a race condition where in just the right circumstances a rendezvous point could man-in-the-middle (impersona
    36Monitor
  • CVE-2026-44603Tor before 0.4.9.7 has an out-of-bounds read by one byte via a malformed BEGIN cell, aka TROVE-2026-007.
    36Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2020-15572Jul 15, 2020 · Tor before 0.4.3.6 has an out-of-bounds memory access that allows a remote denial-of-service (crash) attack against Tor instances built to u
    30Monitor
  • ← EarlierCVE-2021-28089Mar 19, 2021 · Tor before 0.4.5.7 allows a remote participant in the Tor directory protocol to exhaust CPU resources on a target, aka TROVE-2021-001.
    31Monitor
  • Later →CVE-2021-34548Jun 29, 2021 · An issue was discovered in Tor before 0.4.6.5, aka TROVE-2021-003.
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:tor0.4.5.7-1 · Debian:12Package registry (OSV)
opensuse:tor0.4.5.7-lp152.2.9.1 · openSUSE:Leap 15.2Package registry (OSV)
suse:tor0.4.5.7-bp152.2.9.1 · SUSE:Package Hub 15 SP2Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
low · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
Low

Weakness class (CWE)

CWE-617 · Reachable Assertion

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records