CVE Intelligence
Medium Access control exploit reference

CVE-2021-21290 — Local Information Disclosure Vulnerability in Netty on Unix-Like systems due temporary files

Netty is an open-source, asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. In Netty before version 4.1.59.Final there is a vulnerability on Unix-like systems involving an insecure temp file. When netty's multipart decoders are used local information disclosure can occur via the local system temporary directory if temporary storing uploads on the disk is enabled. On unix-like systems, the temporary directory is shared between all user. As such, writing to this directory using APIs that do not explicitly set the file/directory permissions can lead to information disclosure. Of note, this does not impact modern MacOS Operating Systems. The method "File.createTempFile" on unix-like systems creates a random file, but, by default will create this file with the permissions "-rw-r--r--". Thus, if sensitive information is written to this file, other local users can read this information. This is the case in netty's "AbstractDiskHttpData" is vulnerable. This has been fixed in version 4.1.59.Final. As a workaround, one may specify your own "java.io.tmpdir" when you start the JVM or use "DefaultHttpDataFactory.setBaseDir(...)" to set the directory to something that is only readable by the current user.

Published Feb 8, 2021 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 1.8% (30-day exploitation probability)+12
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
1.78%
ahead of 78% of scored CVEs · Oct 15, 2026
Affects
Debian
Debian Linux and 12 more
CVSS base
5.5
Medium · 3 source(s)
Prioritization reference: 6.2 provisional

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — github.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Debian Debian Linux, Netapp Active Iq Unified Manager, Netapp Cloud Secure Agent…).
  2. Apply the fixed version or the patch documented under Remediation.
  3. Search available logs for exploit probes matching the vulnerability class (access control), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Debian Debian Linux version 10.0version 9.0 Vulnerable NIST National Vulnerability Database
Netapp Active Iq Unified Manager versions not specified by the source Vulnerable NIST National Vulnerability Database
Netapp Cloud Secure Agent versions not specified by the source Vulnerable NIST National Vulnerability Database
Netapp Snapcenter versions not specified by the source Vulnerable NIST National Vulnerability Database
Netty Netty < 4.1.59 Vulnerable NIST National Vulnerability Database
Netty Netty version < 4.1.59.Final Vulnerable CVE Program (cve.org) e CISA ADP
Oracle Banking Corporate Lending Process Management version 14.2.0version 14.3.0version 14.5.0 Vulnerable NIST National Vulnerability Database
Oracle Banking Credit Facilities Process Management version 14.2.0version 14.5.0version 14.3.0 Vulnerable NIST National Vulnerability Database
Oracle Banking Trade Finance Process Management version 14.2.0version 14.3.0version 14.5.0 Vulnerable NIST National Vulnerability Database
Oracle Communications Brm - Elastic Charging Engine version 12.0.0.3 Vulnerable NIST National Vulnerability Database
Oracle Communications Design Studio version 7.4.2 Vulnerable NIST National Vulnerability Database
Oracle Communications Messaging Server version 8.1 Vulnerable NIST National Vulnerability Database
Oracle Nosql Database < 20.3 Vulnerable NIST National Vulnerability Database
Quarkus Quarkus ≤ 1.13.7 Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
6.2 CVSS 3.1 Medium 2.5 3.6 security-advisories@github.com via NIST National Vulnerability Database
6.2 CVSS 3.1 Medium — — GitHub_M via CVE Program (cve.org) e CISA ADP
5.5 CVSS 3.1 Medium 1.8 3.6 nvd@nist.gov via NIST National Vulnerability Database
1.9 CVSS 2.0 Low 3.4 2.9 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N (score shown at the top: nvd@nist.gov)
Scoring entities (NIST, CNA, ADP) score independently; each score is shown with its origin. For prioritization we use 6.2 (security-advisories@github.com via NIST National Vulnerability Database) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-668 · Exposure of Resource to Wrong Sphere

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 1.78%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
  • Audit administrative actions and access to resources outside each user’s normal pattern.
endpoint telemetry (EDR)authentication logsapplication logs

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · netty/netty
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 5.5
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Modified
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • 2021
  • CVE published
    Feb 8, 2021 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

39 on the record

Elsewhere on this site

Debian
every CVE for this vendor
Access control
same class
CWE-668
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-100663 Netty HTTP/1 CONNECT authority-form mistranslated to malformed HTTP/3 19d
  • CVE-2026-100664 Netty 4.2.2 through 4.2.17 HTTP/1 Host Header Authority Confusion 19d
  • CVE-2026-100665 Netty 4.2.11 through 4.2.17 QUIC Hostname Verification Bypass 19d
  • CVE-2026-100666 Netty 4.2.0 through 4.2.16 Response Desynchronization via HttpServerCodec 19d
  • CVE-2026-100662 Netty HTTP/3 QPACK encoder-stream unbounded memory exhaustion DoS 19d
  • CVE-2026-100661 Netty HTTP/3 QPACK Prefixed Integer DoS via Unbounded Accumulation 19d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2021-21290 is "Local Information Disclosure Vulnerability in Netty on Unix-Like systems due temporary files", rated Medium. It affects Debian Linux (Debian); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.5 describes technical severity. EPSS 1.78% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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