🛡️ CVE-2021-22947 on Debian — curl

⚪ Unknown ✅ No Known Exploit OSV

N/A

CVSS Score

0 Low4 Medium7 High9 Critical10

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.

Distribution advisory

This page covers CVE-2021-22947 as tracked by Debian, for the package curl. The fix is available in version 7.79.1-1; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity high, availability none.

Affected software

DEBIAN-CVE-2021-22947 is recorded against 1 package.

curl (fixed in 7.79.1-1)

Timeline and source

Published on 29 September 2021 and last revised on 4 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security-tracker.debian.org (Advisory)

CVE-2021-22947 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Alpine Ubuntu

Details

Severity Unknown

CVSS Score N/A

CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

CWE N/A

Public Exploit ✅ No

Source OSV

Published 2021-09-29

Updated 2026-08-20

Modified 2026-08-04

Fix URL N/A

Affected Packages

Software	From version	Fixed in
curl	—	7.79.1-1

References

ADVISORY https://security-tracker.debian.org/tracker/CVE-2021-22947

🔗 NVD 🔗 Mitre

Similar Threats

Free Vulnerability Check

Is your site affected by DEBIAN-CVE-2021-22947?

BotEraser helps you identify potentially vulnerable plugins and themes by checking your installation against DEBIAN-CVE-2021-22947 and other known CVE records.

Scan My Site Free →

No credit card required · Results in minutes

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.