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CVE Record

CVE-2021-23409: Denial of Service (DoS)

The package github.com/pires/go-proxyproto before 0.6.0 are vulnerable to Denial of Service (DoS) via creating connections without the proxy protocol header.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This CVE affects a Go library used to parse PROXY protocol headers. Versions before 0.6.0 could be forced into a denial-of-service condition by connections that omit the expected header. The business impact is availability loss for services relying on this library in exposed network paths.

Executive priority

Treat as high priority for internet-facing or critical network services because it can affect availability without authentication. Internal-only use lowers urgency, but dependency verification should still be completed promptly.

Technical view

github.com/pires/go-proxyproto before v0.6.0 is vulnerable to network-triggered DoS when handling connections without a PROXY protocol header. The CVSS 3.1 score is 7.5, reflecting unauthenticated, low-complexity, remote availability impact. The source bundle identifies v0.6.0 as the relevant fixed release.

Likely exposure

Exposure is most likely in Go services, proxies, load-balancer integrations, or network listeners importing github.com/pires/go-proxyproto below v0.6.0, especially where untrusted clients can open TCP connections.

Exploitation context

CISA KEV is false in the supplied bundle, and no cited source establishes active exploitation. The described condition is remotely reachable and unauthenticated, but the provided evidence does not show public exploitation or affected downstream products.

Researcher notes

The bundle does not list a CWE and gives limited implementation detail beyond missing PROXY protocol headers. Focus analysis on dependency reachability, listener exposure, and whether services accept direct client connections instead of only trusted proxy traffic.

Mitigation direction

  • Upgrade github.com/pires/go-proxyproto to v0.6.0 or later.
  • Inventory Go modules and transitive dependencies for vulnerable versions.
  • Prioritize services exposed to untrusted network traffic.
  • Check upstream release notes and vendor guidance for deployment-specific considerations.

Validation and detection

  • Inspect go.mod and dependency lock data for go-proxyproto versions below 0.6.0.
  • Confirm production builds resolve to v0.6.0 or later.
  • Identify public or partner-facing listeners using this library.
  • Review availability metrics for unexplained connection-driven service degradation.
Prepared
Confidence
high
Sources
7

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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CVE-2021-23409 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

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

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
6Source 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
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2021-23409Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

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
n/agithub.com/pires/go-proxyprotounspecifiedListed
Weakness

CWE details

No CWE listed

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