Vigie VulnDBEuropean-hosted Vulnerability DB

CVE-2021-22947

At a glance

Severity
MEDIUM 5.9
EPSS
EPSS 3.01 % · percentile 87 (2026-10-27)
State
PUBLISHED
Published
Updated
Assigner
hackerone
NVD status
Modified

Description

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.

Scores

VersionScoreVectorScored by
CVSS 3.1MEDIUM 5.9CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:NCISA-ADP
CVSS 3.1MEDIUM 5.9CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:NNVD · nvd@nist.gov (Primary)
CVSS 3.1MEDIUM 5.9CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:NNVD · 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Secondary)
CVSS 2.0MEDIUM 4.3AV:N/AC:M/Au:N/C:N/I:P/A:NNVD · nvd@nist.gov (Primary)

Weaknesses (CWE)

European references

CERT-FR advisories

Affected configurations (NVD CPE)

Affected products

ProductVersions
https://github.com/curl/curlaffected curl 7.20.0 to and including 7.78.0

References

Sources

SourceLicence
CVE List (CVEProject cvelistV5)CVE Program Terms of Use
EPSS (FIRST.org)FIRST — attribution requested
ENISA EUVDENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feedsPublic domain — this product uses data from the NVD API but is not endorsed or certified by the NVD