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CVE-2021-28090· NVD / CVE Program· CNA mitre

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.

MediumCVSS 5.3 · v3.1—No exploit Fix available
Published
Mar 19, 2021
Updated
Jun 16, 2026
EPSS
2.1% · 81th percentile
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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 · 2.1%

Affected systems

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

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
  • CVE-2026-44597Tor before 0.4.9.7 has an out-of-bounds read when an END, a TRUNCATE, or a TRUNCATED cell lacks a reason in its payload, aka TROVE-2026-011.
    36Monitor
  • CVE-2018-0491A use-after-free issue was discovered in Tor 0.3.2.x before 0.3.2.10.
    34Monitor
  • CVE-2026-77641tor before 0.4.9.9 was prone to a NULL write after free when sending a CONFLUX_SWITCH cell fails.
    32Monitor

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.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

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.

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.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

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Change log

  1. Fix✗ → ✓

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References

All records