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CVE Record

CVE-2021-28169: For Eclipse Jetty versions <= 9.4.40, <= 10.0.2, <= 11.0.2, it is possible for requests to the ConcatServle...

For Eclipse Jetty versions <= 9.4.40, <= 10.0.2, <= 11.0.2, it is possible for requests to the ConcatServlet with a doubly encoded path to access protected resources within the WEB-INF directory. For example a request to `/concat?/%2557EB-INF/web.xml` can retrieve the web.xml file. This can reveal sensitive information regarding the implementation of a web application.

MediumCVSS 5.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-28169 lets an unauthenticated remote requester use Jetty's ConcatServlet to read protected WEB-INF files when paths are doubly encoded. The business risk is disclosure of application internals, configuration, or deployment details, not direct code execution. Treat internet-facing Jetty apps using ConcatServlet as priority patch candidates.

Executive priority

Prioritize remediation for internet-facing Jetty applications because the issue is remotely reachable without authentication. It is moderate severity because impact is limited to information disclosure, but exposed configuration details can support later compromise.

Technical view

Jetty versions <= 9.4.40, <= 10.0.2, and <= 11.0.2 mishandle doubly encoded paths in ConcatServlet, allowing access to protected WEB-INF resources. CVSS 3.1 is 5.3 with network access, low complexity, no privileges, no user interaction, and low confidentiality impact only.

Likely exposure

Exposure is most likely where Jetty serves web applications that enable or package ConcatServlet, especially public applications with sensitive WEB-INF metadata. The source bundle does not prove all Jetty deployments are exploitable.

Exploitation context

The bundle provides a request pattern example and marks KEV as false. No cited source in the bundle supports active exploitation in the wild, so exploitation should be treated as plausible but not confirmed.

Researcher notes

Focus triage on ConcatServlet reachability and protected WEB-INF resource exposure. Do not assume arbitrary file read or code execution from this CVE alone. Downstream Apache Kafka and ZooKeeper references show dependency-driven exposure and upgrades, not independent product-specific exploit details.

Mitigation direction

  • Upgrade Jetty beyond the affected versions using Eclipse vendor guidance.
  • For Jetty 9.4 deployments, downstream sources reference upgrades to 9.4.41 or 9.4.42.
  • Review packaged applications such as Kafka or ZooKeeper for bundled Jetty dependencies.
  • Restrict or disable ConcatServlet where it is unnecessary.
  • Avoid exposing Jetty management or application surfaces directly to the internet.

Validation and detection

  • Inventory applications and transitive dependencies using Eclipse Jetty.
  • Confirm whether ConcatServlet is enabled or reachable in deployed web applications.
  • Check Jetty versions against <= 9.4.40, <= 10.0.2, and <= 11.0.2.
  • Review logs for unusual encoded requests targeting WEB-INF resources.
  • Verify downstream products have applied their Jetty security updates.
Prepared
Confidence
high
Sources
8

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · medium confidence lookup

CWE-200: Information exposure and cloud metadata lookup

Information exposure and SSRF weaknesses can make discovery, cloud metadata, and credential material review relevant. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2021-28169 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.3 (3.1)
Known Exploited
No
Published

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

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.

1CVSS vectors
0Timeline events
0ADP providers
25Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.3CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N3.91.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

5.3Medium
CVSS 3.1 vector shape for CVE-2021-28169Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
The Eclipse FoundationEclipse Jettyunspecified, unspecified, unspecifiedListed
Weakness

CWE details

CWE-200

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

CWE-200 · source CWE mapping

Exposure of Sensitive Information to an Unauthorized Actor

Exposure of Sensitive Information to an Unauthorized Actor represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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