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CVE Record

CVE-2021-22924: libcurl keeps previously used connections in a connection pool for subsequenttransfers to reuse, if one of...

libcurl keeps previously used connections in a connection pool for subsequenttransfers to reuse, if one of them matches the setup.Due to errors in the logic, the config matching function did not take 'issuercert' into account and it compared the involved paths *case insensitively*,which could lead to libcurl reusing wrong connections.File paths are, or can be, case sensitive on many systems but not all, and caneven vary depending on used file systems.The comparison also didn't include the 'issuer cert' which a transfer can setto qualify how to verify the server certificate.

LowCVSS 3.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

This is a low-severity libcurl flaw where secure connections could be reused when they should not be. In unusual configurations, libcurl might treat two transfers as equivalent even when issuer-certificate verification settings or case-sensitive certificate paths differ, creating a limited confidentiality risk.

Executive priority

Treat as routine patch management unless affected libcurl is used in sensitive outbound TLS workflows. It is not supported by the provided sources as actively exploited, but it is broadly relevant because curl is widely embedded.

Technical view

libcurl 7.10.4 through 7.77.0 could incorrectly match reusable connections because the matching logic ignored issuercert and compared involved paths case-insensitively. On systems with case-sensitive paths, or transfers relying on issuer certificate constraints, a later transfer could reuse an inappropriate existing connection.

Likely exposure

Exposure is most likely in applications, appliances, containers, or OS packages that embed affected curl/libcurl versions and perform multiple HTTPS transfers with connection reuse plus issuer certificate or path-sensitive verification differences.

Exploitation context

The bundle does not cite active exploitation, and KEV is false. CVSS marks attack complexity high with only low confidentiality impact. Practical abuse appears dependent on specific libcurl configuration and connection reuse behavior.

Researcher notes

Focus validation on libcurl connection cache behavior and TLS verification configuration. The core issue is equivalence matching for connection reuse, specifically missing issuercert comparison and case-insensitive path comparison where path semantics may differ.

Mitigation direction

  • Inventory curl and embedded libcurl versions across hosts, containers, and vendor appliances.
  • Apply relevant vendor security updates from OS or product suppliers.
  • Move upstream curl/libcurl outside the affected 7.10.4 through 7.77.0 range where applicable.
  • Check vendor advisories for Oracle, NetApp, Siemens, Debian, Fedora, and bundled products.
  • Prioritize internet-facing services that make repeated outbound TLS requests.

Validation and detection

  • Confirm no deployed curl/libcurl version remains within 7.10.4 through 7.77.0.
  • Review SBOMs and container images for statically linked libcurl copies.
  • Identify applications using issuer certificate settings with pooled or reused connections.
  • Verify distro package changelogs reference CVE-2021-22924 remediation.
  • Document accepted risk where vendor firmware remains pending.
Prepared
Confidence
medium
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

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ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-20: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-22924 mapping review

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Vulnerability profileCVE Program record
Severity
Low
CVSS
3.7 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/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
16Source 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
3.7CVSS 3.1LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N2.21.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

3.7Low
CVSS 3.1 vector shape for CVE-2021-22924Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:H/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
n/ahttps://github.com/curl/curlcurl 7.10.4 to and include curl 7.77.0Listed
Weakness

CWE details

CWE-20

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

CWE-20 · source CWE mapping

Improper Input Validation

Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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