Answer in brief
CVE-2021-22947 records a Medium severity (CVSS 5.9) vulnerability in CVE Program Container. The current sources do not mark it as known exploited. The current feed maps n/a/https://github.com/curl/curl (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (generic), Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.9. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps n/a/https://github.com/curl/curl (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (generic), Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| n/a/https://github.com/curl/curlgeneric | curl 7.20.0 to and including 7.78.0 | Not reported |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.0 <V3.1.5 | V3.1.5 |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.0 <V3.1.5 | V3.1.5 |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.0 <V3.1.5 | V3.1.5 |
Published upstream
Sep 29, 2021
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 14, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Oct 14, 2026
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.
Quoted source text, attributed separately from HOL analysis.