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Vulnerabilities/CVE-2021-22947Public Intelligence Dossier
Source: haxx · Limited verification•Last verified: •Collection Degraded
CVE-2021-22947Unknown / EvaluatingMEDIUM (raw)CVSS 5.9CWE-310

When curl >= 7.20.0 and <= 7.78.0 connects to an IMAP or POP3 server to retrieve data using STARTTLS to upgrade to TLS security, the server can respond and send back multiple responses at once that curl caches

Published: 30 Sept 2021•Last updated: 14 Oct 2026, 05:47 PM IST•Source identifier: support@hackerone.com
Dossier completeness: source-provided sections 2 / 3 · rule guidance available. Missing source facts count as incomplete.
Official source
CISA KEV catalog
Unknown
KEV status was not determined.
CVSS score
5.9MEDIUM (raw)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Metric sourcenvd@nist.gov
EPSS probability
3%0.030
Percentile87th
Weakness type
CWE-310
CWE-345
Remediation
Patch status unknown
No fixed version or KB recorded

Why It Matters

Analysis dossier

Why It Matters

When curl >= 7.20.0 and <= 7.78.0 connects to an IMAP or POP3 server to retrieve data using STARTTLS to upgrade to TLS security, the server can respond and send back multiple responses at once that curl caches. curl would then upgrade to TLS but not flush the in-queue of cached responses but instead continue using and trustingthe responses it got *before* the TLS handshake as if they were authenticated.Using this flaw, it allows a Man-In-The-Middle attacker to first inject the fake responses, then pass-through the TLS traffic from the legitimate server and trick curl into sending data back to the user thinking the attacker's injected data comes from the TLS-protected server.

SOC priority

Medium

Actively exploited

Unknown

Publicly disclosed

Unknown

Risk basis: Microsoft or Microsoft-managed product relevance; No confirmed exploitation signal in current enrichment

Affected Products & Remediation

26 source-backed products
Affected products and versions (source)
  • haxx curl · >= 7.20.0 < 7.79.0 · NVD CPE · Source
  • fedoraproject fedora · 33; 35 · NVD CPE · Source
  • debian debian linux · 9.0; 10.0; 11.0 · NVD CPE · Source
  • netapp cloud backup · version range not provided by source · NVD CPE · Source
  • netapp clustered data ontap · version range not provided by source · NVD CPE · Source
  • netapp h300s firmware · version range not provided by source · NVD CPE · Source
  • netapp h500s firmware · version range not provided by source · NVD CPE · Source
  • netapp h700s firmware · version range not provided by source · NVD CPE · Source
  • netapp h300e firmware · version range not provided by source · NVD CPE · Source
  • netapp h500e firmware · version range not provided by source · NVD CPE · Source
  • netapp h700e firmware · version range not provided by source · NVD CPE · Source
  • netapp h410s firmware · version range not provided by source · NVD CPE · Source
  • netapp solidfire baseboard management controller firmware · version range not provided by source · NVD CPE · Source
  • oracle communications cloud native core binding support function · 1.11.0; 22.1.3 · NVD CPE · Source
  • oracle communications cloud native core network function cloud native environment · 1.10.0 · NVD CPE · Source
  • oracle communications cloud native core network repository function · 1.15.0; 1.15.1; 22.1.2; 22.2.0 · NVD CPE · Source
  • oracle communications cloud native core network slice selection function · 1.8.0 · NVD CPE · Source
  • oracle communications cloud native core service communication proxy · 1.15.0 · NVD CPE · Source
  • oracle mysql server · >= 5.7.0 <= 5.7.35; >= 8.0.0 <= 8.0.26 · NVD CPE · Source
  • oracle peoplesoft enterprise peopletools · 8.57; 8.58; 8.59 · NVD CPE · Source
  • siemens sinec infrastructure network services · < 1.0.1.1 · NVD CPE · Source
  • apple macos · < 12.3 · NVD CPE · Source
  • oracle commerce guided search · 11.3.2 · NVD CPE · Source
  • oracle communications cloud native core console · 22.2.0 · NVD CPE · Source
  • oracle communications cloud native core security edge protection proxy · 22.1.1 · NVD CPE · Source
  • splunk universal forwarder · >= 8.2.0 < 8.2.12; >= 9.0.0 < 9.0.6; 9.1.0 · NVD CPE · Source
NVD applicability prerequisites: cpe:2.3:h:netapp:h300s:-:*:*:*:*:*:*:*, cpe:2.3:h:netapp:h500s:-:*:*:*:*:*:*:*, cpe:2.3:h:netapp:h700s:-:*:*:*:*:*:*:*, cpe:2.3:h:netapp:h300e:-:*:*:*:*:*:*:*, cpe:2.3:h:netapp:h500e:-:*:*:*:*:*:*:*, cpe:2.3:h:netapp:h700e:-:*:*:*:*:*:*:*, cpe:2.3:h:netapp:h410s:-:*:*:*:*:*:*:*, cpe:2.3:h:netapp:solidfire_baseboard_management_controller:-:*:*:*:*:*:*:*. These are conditions, not proof that an environment is exposed or unaffected.
Recorded patch / KBNot provided by source

Vendor or catalog guidance (source)

Not provided by source

Known exploitation (source facts)

Only what a source states. Unknown means no source has said either way; it is not "not exploited".

CISA KEV
Unknown
Exploited (source statement)
Unknown
Publicly disclosed (source)
Unknown

Suggested hunting (rule-based inference)

SecOps Signal recommendation (rule-based inference). These steps are hunting hypotheses from the vulnerability class; they do not state or imply that exploitation occurred here or anywhere.

Matched network-unauthenticated (CVSS AV:N, CVSS PR:N, CVSS UI:N)

Exposure

  1. Identify devices reporting this CVE and note which expose the affected service to untrusted networks.Telemetry: DeviceTvmSoftwareVulnerabilities · A network-reachable, no-privilege vector makes internet-facing instances the first exposure question. · Rule network-unauthenticated

Exploitation evidence

  1. Review inbound connections to the affected service from unexpected sources since the advisory date.Telemetry: DeviceNetworkEvents · Hunting hypothesis from the CVSS vector; it does not show that exploitation occurred. · Rule network-unauthenticated

Response

  1. Confirm the source-stated update is installed and the CVE is no longer reported.Telemetry: DeviceTvmSoftwareVulnerabilities · A follow-up inventory check verifies remediation. · Rule network-unauthenticated

CISA KEV Record

CISA KEV status was not determined for this record.

Change History & Source Data

— No recorded material change

CNA / source
support@hackerone.com
Record status · verification
UPDATED · NVD API
CPE
cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*, cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*, cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*, cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*, cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*, cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*, cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:*, cpe:2.3:a:netapp:clustered_data_ontap:-:*:*:*:*:*:*:*, cpe:2.3:o:netapp:h300s_firmware:-:*:*:*:*:*:*:*, cpe:2.3:h:netapp:h300s:-:*:*:*:*:*:*:*

Evidence & Provenance

3 public sources
cert-portal.siemens.comSource recordnvd.nist.govSource recordhackerone.comSource record

Linked by the query's stored exact CVE association. Review required tables and validation status before use.

Detection Hunting Query
Target: DeviceTvmSoftwareVulnerabilities•Defender XDR
Detect endpoints exposed to CVE-2021-22947
Purpose: Exposure assessment (Category: Exposure Check)Why linked: Query metadata names CVE-2021-22947
DeviceTvmSoftwareVulnerabilities| where CveId == "CVE-2021-22947"| project DeviceId, DeviceName, OSPlatform, OSVersion, SoftwareVendor, SoftwareName, SoftwareVersion, CveId, VulnerabilitySeverityLevel, RecommendedSecurityUpdate, RecommendedSecurityUpdateId| sort by VulnerabilitySeverityLevel desc
Schema Checked · Not runtime validatedSource: SecOps Signal deterministic template · Limited verificationStatic screening: Passed structure and schema checks; tenant execution is not verified.
Open KQL Library

Correlated briefings

— No published briefing references this CVE

SecOps Signal surfaces public advisory facts only. A missing value means the source has not published it, not that your environment is unaffected. No tenant inventory is connected.