CVE-2021-22947

MEDIUMNVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

Score 5.9 from GitHub Security Advisory published 2022-05-24. NVD baseline CVSS 5.9; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Elevated
5.9
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 3%CVSS: 5.9Exploit: NoneExposed: 0

A fix is available — apply it.

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.

CVSS v3
5.9
EG Score
5.9(medium)
EG Risk
43(Track)
EG Risk 43/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity59% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
85.0%
KEV
Not listed

Published

September 29, 2021

Last Modified

April 16, 2026

References (30)

Patch Availability(5)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntucurl (7.74.0-1ubuntu2.3) @ hirsute2026-05-22ubuntu
ubuntulibcurl4-openssl-dev (7.47.0-1ubuntu2.19+esm1) @ xenial2026-05-22ubuntu
redhatrh-dotnet31-curl-0:7.61.1-22.el7_92022-04-13redhat
redhatcurl-0:7.61.1-12.el8_2.42022-02-22redhat
redhatcurl-0:7.61.1-18.el8_4.22021-11-02redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(6)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 10× in last 7d / 46× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 141 total refreshes for this CVE.

  1. 2026-07-23 01:57 UTCEG score recompute
  2. 2026-07-22 22:44 UTCEG score recompute
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Frequently asked(5)

What is CVE-2021-22947?
CVE-2021-22947 is a medium vulnerability published on September 29, 2021. 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…
When was CVE-2021-22947 disclosed?
CVE-2021-22947 was first published in the National Vulnerability Database on September 29, 2021, with the most recent update on April 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-22947 actively exploited?
CVE-2021-22947 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 85.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-22947?
CVE-2021-22947 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2021-22947?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-22947, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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