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CVE-2021-20796· NVD / CVE Program· CNA jpcert

Directory traversal vulnerability in the management screen of Cybozu Remote Service 3.1.8 allows a remote authenticated attacker to upload a

Directory traversal vulnerability in the management screen of Cybozu Remote Service 3.1.8 allows a remote authenticated attacker to upload an arbitrary file via unspecified vectors.

MediumCVSS 6.5 · v3.1—No exploit No fix recorded
Published
Oct 13, 2021
Updated
Jun 16, 2026
EPSS
1.5% · 74th percentile
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Report tools

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Action score

26

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.5%

Noroxi analysis

No Noroxi analysis for this record yet

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Affected systems

VendorProduct
cybozuremote service manager

Affected versions

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

  • cybozu remote service manager3.1.8

Versions reported by the vendor

Affected version ranges reported by the assigning authority (jpcert). Independent of NVD's CPE analysis and usually ahead of it.

  • Cybozu, Inc. Cybozu Remote Service

    • 3.1.8affected

Same product

cybozu: all records

Other highest-scoring records for the same primary product.

  • CVE-2018-16171Directory traversal vulnerability in Cybozu Remote Service 3.0.0 to 3.1.8 allows remote attackers to execute Java code file on the server vi
    36Monitor
  • CVE-2021-20795Cross-site request forgery (CSRF) vulnerability in the management screen of Cybozu Remote Service 3.1.8 to 3.1.9 allows a remote attacker to
    35Monitor
  • CVE-2018-16169Cybozu Remote Service 3.0.0 to 3.1.0 allows remote authenticated attackers to upload and execute Java code file on the server via unspecifie
    35Monitor
  • CVE-2018-16170Directory traversal vulnerability in Cybozu Remote Service 3.0.0 to 3.1.8 for Windows allows remote authenticated attackers to read arbitrar
    33Monitor
  • CVE-2014-7266Algorithmic complexity vulnerability in Cybozu Remote Service Manager through 2.3.0 and 3.x through 3.1.2 allows remote attackers to cause a
    32Monitor
  • CVE-2014-1983Unspecified vulnerability in Cybozu Remote Service Manager through 2.3.0 and 3.x before 3.1.1 allows remote attackers to cause a denial of s
    32Monitor

Remediation

Which version to upgrade to

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

No fix version is recorded for this entry. Check the references for vendor advisories.

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.

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

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
High
Availability impact
None

Weakness class (CWE)

CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CVSS vector

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

nvd-primary

Root cause

A user-supplied file name is joined with the allowed directory, but the result is never checked to confirm it is still inside that directory.

The bug in code

The whole CWE-22 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
const file = path.join(ROOT, req.query.name);res.sendFile(file);

Fixed

ts
const file = path.resolve(ROOT, req.query.name);if (!file.startsWith(ROOT + path.sep)) {  return res.sendStatus(400);}res.sendFile(file);

Attack context

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

ATT&CK techniques

—

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

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

All records