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CVE-2021-22946: A user can tell curl >= 7.20.0 and <= 7.78.0 to require a successful upgrade to TLS when speaking to an IMAP,

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This week
HIGH 7.5REMOTEWATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2021-22946 is a high-severity flaw (CVSS 7.5) affecting curl, debian linux, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A user can tell curl >= 7.20.0 and <= 7.78.0 to require a successful upgrade to TLS when speaking to an IMAP, POP3 or FTP server (`--ssl-reqd` on the command line or`CURLOPT_USE_SSL` set to `CURLUSESSL_CONTROL` or `CURLUSESSL_ALL` withlibcurl). This requirement could be bypassed if the server would return a properly crafted but perfectly legitimate response.This flaw would then make curl silently continue its operations **withoutTLS** contrary to

Why this priority

  • High severity
  • EPSS top 8%: very likely to be exploited
  • Public exploit reference
  • Remotely exploitable, no login, no user action
  • On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score7.5 (High)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance4.5% (top 8%)
CISA exploited listNo
WeaknessCWE-325, CWE-319
Published2021-09-29
Last modified2026-10-14
Publisher (CNA): HackerOne · Vendor: debian · fedoraproject · haxx · netapp

Share: LinkedIn · X · Reddit

Last updated 2026-10-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

haxx curl UPGRADE
Affected: >= 7.20.0 and < 7.79.0
Fixed in: 7.79.0
Safe to downgrade to: a release before 7.20.0
1. Check installed version
apt-cache policy curl || rpm -q curl || curl --version
2. UPGRADE to 7.79.0 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade curl
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade curl
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 7.20.0 (Debian / Ubuntu)
apt-cache madison curl sudo apt install curl=<VERSION_BEFORE_7.20.0> sudo apt-mark hold curl
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list curl sudo dnf downgrade curl-<VERSION_BEFORE_7.20.0> sudo dnf versionlock add curl
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
debian debian linux MITIGATE
Affected: 9.0 · 10.0 · 11.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 9.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
fedoraproject fedora MITIGATE
Affected: 33 · 35
Fixed in: no fixed release known
Safe to downgrade to: a release before 33
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
netapp cloud backup MITIGATE
Affected: all versions
Fixed in: no fixed release known
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy cloud-backup || rpm -q cloud-backup || cloud-backup --version
No fixed or unaffected release known
Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.
netapp clustered data ontap MITIGATE
Affected: all versions
Fixed in: no fixed release known
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy clustered-data-ontap || rpm -q clustered-data-ontap || clustered-data-ontap --version
No fixed or unaffected release known
Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.
netapp oncommand insight MITIGATE
Affected: all versions
Fixed in: no fixed release known
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy oncommand-insight || rpm -q oncommand-insight || oncommand-insight --version
No fixed or unaffected release known
Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-22946?

curl: upgrade to 7.79.0; debian linux: mitigate or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-22946 being exploited?

CVE-2021-22946 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-22946 affect?

CVE-2021-22946 affects curl, debian linux, fedora. Severity is high (CVSS 7.5). A user can tell curl >= 7.20.0 and <= 7.78.0 to require a successful upgrade to TLS when speaking to an IMAP, POP3 or FTP server (`--ssl-reqd` on the command line or`CURLOPT_USE_SSL` set to `CURLUSESSL_CONTROL` or `CURLUSESSL_ALL` withlibcu

How urgent is CVE-2021-22946?

Priority 64/100. High severity; EPSS top 8%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Debian vulnerabilities · curl vulnerabilities

Related CVEs

References

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