ALPINE-CVE-2021-22947 — Vulnetix

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ALPINE-CVE-2021-22947 PUBLISHED CVSS 5.900000095367432 MEDIUM

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.

Risk Scores

CVSS v3.1

5.900000095367432

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

Affected Products

Vendor	Product	Versions
Alpine:v3.16	curl	7.66.0-r0, 7.25.0-r0, 7.26.0-r0
Alpine:v3.11	curl	7.54.0-r0, 7.54.1-r0, 7.55.0-r0
Alpine:v3.13	curl	7.52.1-r0, 0, 7.19.2-r0
Alpine:v3.21	curl	7.22.0-r0, 7.21.7-r2, 7.21.7-r1
Alpine:v3.19	curl	7.26.0-r0, 7.78.0-r0, 7.77.0-r1
Alpine:v3.22	curl	7.19.2-r0, 7.19.2-r1, 7.19.4-r0
Alpine:v3.12	curl	7.40.0-r0, 0, 7.19.2-r0
Alpine:v3.20	curl	7.42.1-r0, 7.42.1-r1, 7.43.0-r0
Alpine:v3.23	curl	0, 7.22.0-r0, 7.21.7-r2
Alpine:v3.18	curl	7.23.1-r0, 7.24.0-r0, 7.25.0-r0
Alpine:v3.17	curl	7.78.0-r2, 7.78.0-r1, 7.78.0-r0
Alpine:v3.14	curl	7.47.0-r0, 7.78.0-r0, 7.77.0-r1
Alpine:v3.15	curl	7.78.0-r2, 0, 7.19.2-r0

Timeline

Sep 29, 2021 CVE Published
Dec 3, 2025 CVE Updated
Apr 30, 2026 Distribution Patch

References

https://security.alpinelinux.org/vuln/CVE-2021-22947 advisory

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