CVE-2021-22947 — When curl >= 7.20.0 and <= 7.78.0 connects to an IMAP or POP3 server to retrieve data using...
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.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 3% (30-day exploitation probability)+13
- Technical severity (medium)+3
- CISA SSVC: exploitation "poc"+5
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — cert-portal.siemens.com (NIST National Vulnerability Database)
- Documented patch — www.oracle.com (NIST National Vulnerability Database)
- Documented patch — www.oracle.com (NIST National Vulnerability Database)
- Documented patch — www.oracle.com (NIST National Vulnerability Database)
- Documented patch — www.oracle.com (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Apple Macos, Debian Debian Linux, Fedoraproject Fedora…).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- Apply the fixed version or the patch documented under Remediation.
- Search available logs for exploit probes matching the vulnerability class (integrity), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Apple | Macos | < 12.3 | Vulnerable | NIST National Vulnerability Database |
| Debian | Debian Linux | version 9.0version 10.0version 11.0 | Vulnerable | NIST National Vulnerability Database |
| Fedoraproject | Fedora | version 35version 33 | Vulnerable | NIST National Vulnerability Database |
| Haxx | Curl | ≥ 7.20.0 and < 7.79.0 | Vulnerable | NIST National Vulnerability Database |
| Netapp | Cloud Backup | versions not specified by the source | Vulnerable | NIST National Vulnerability Database |
| Netapp | Clustered Data Ontap | versions not specified by the source | Vulnerable | NIST National Vulnerability Database |
| Netapp | H300e Firmware | versions not specified by the source | Vulnerable | NIST National Vulnerability Database |
| Netapp | H300s Firmware | versions not specified by the source | Vulnerable | NIST National Vulnerability Database |
| Netapp | H410s Firmware | versions not specified by the source | Vulnerable | NIST National Vulnerability Database |
| Netapp | H500e Firmware | versions not specified by the source | Vulnerable | NIST National Vulnerability Database |
| Netapp | H500s Firmware | versions not specified by the source | Vulnerable | NIST National Vulnerability Database |
| Netapp | H700e Firmware | versions not specified by the source | Vulnerable | NIST National Vulnerability Database |
| Netapp | H700s Firmware | versions not specified by the source | Vulnerable | NIST National Vulnerability Database |
| Netapp | Solidfire Baseboard Management Controller Firmware | versions not specified by the source | Vulnerable | NIST National Vulnerability Database |
| Oracle | Commerce Guided Search | version 11.3.2 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Communications Cloud Native Core Binding Support Function | version 22.1.3version 1.11.0 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Communications Cloud Native Core Console | version 22.2.0 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Communications Cloud Native Core Network Function Cloud Native Environment | version 1.10.0 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Communications Cloud Native Core Network Repository Function | version 1.15.0version 1.15.1version 22.1.2version 22.2.0 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Communications Cloud Native Core Network Slice Selection Function | version 1.8.0 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Communications Cloud Native Core Security Edge Protection Proxy | version 22.1.1 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Communications Cloud Native Core Service Communication Proxy | version 1.15.0 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Mysql Server | ≥ 5.7.0 and ≤ 5.7.35≥ 8.0.0 and ≤ 8.0.26 | Vulnerable | NIST National Vulnerability Database |
| Oracle | Peoplesoft Enterprise Peopletools | version 8.59version 8.58version 8.57 | Vulnerable | NIST National Vulnerability Database |
| Siemens | Sinec Infrastructure Network Services | < 1.0.1.1 | Vulnerable | NIST National Vulnerability Database |
| Splunk | Universal Forwarder | ≥ 8.2.0 and < 8.2.12≥ 9.0.0 and < 9.0.6version 9.1.0 | Vulnerable | NIST National Vulnerability Database |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 5.9 | CVSS 3.1 | Medium | 2.2 | 3.6 | nvd@nist.gov via NIST National Vulnerability Database |
| 5.9 | CVSS 3.1 | Medium | 2.2 | 3.6 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database |
| 5.9 | CVSS 3.1 | Medium | — | — | GitHub, Inc. via GitHub Security Advisories |
| 5.9 | CVSS 3.1 | Medium | — | — | CISA-ADP via CVE Program (cve.org) e CISA ADP |
| 4.3 | CVSS 2.0 | Medium | 8.6 | 2.9 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N (score shown at the top: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 3.01%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Timeline
What happened to this CVE, newest first.
- 2026
- SSVC assessment updated
- Record published
- Fix documented
- Affected products added · haxx/curl, fedoraproject/fedora, debian/debian linux, netapp/cloud backup, netapp/clustered data ontap, netapp/h300s fir
- CVSS changed · 5.9
- Source status changed · → Modified
- Record created in this database
- 2021
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 2× References added · Oct 14, 2026 – Oct 14, 2026
- 1× Official description updated · Oct 14, 2026 – Oct 14, 2026
References
24 on the record
- www.oracle.com/security-alerts/cpuoct2021.html
- www.oracle.com/security-alerts/cpuapr2022.html
- cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf
- www.oracle.com/security-alerts/cpujul2022.html
- www.oracle.com/security-alerts/cpujan2022.html
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/APOAK4
- www.debian.org/security/2022/dsa-5197
- lists.debian.org/debian-lts-announce/2021/09/msg00022.html
- lists.debian.org/debian-lts-announce/2022/08/msg00017.html
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/APOA
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RWLE
- support.apple.com/kb/HT213183
- hackerone.com/reports/1334763
- security.netapp.com/advisory/ntap-20211029-0003
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/RWLEC6
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/APOA
- cert-portal.siemens.com/productcert/html/ssa-398330.html
- cert-portal.siemens.com/productcert/html/ssa-389290.html
- github.com/advisories/GHSA-94jh-wwgf-cmmc
- security.gentoo.org/glsa/202212-01
- security.netapp.com/advisory/ntap-20211029-0003/
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RWLE
- nvd.nist.gov/vuln/detail/CVE-2021-22947
- seclists.org/fulldisclosure/2022/Mar/29
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-86950 Apple Multiple Products Out-of-Bounds Write Vulnerability KEV 17d
- High CVE-2026-83014 Improper Access Control in Oracle Peoplesoft Enterprise Peopletools Sep 15, 2026
- High CVE-2026-83017 Improper Access Control in Oracle Peoplesoft Enterprise Peopletools Sep 15, 2026
- High CVE-2026-83018 Improper Access Control in Oracle Peoplesoft Enterprise Peopletools Sep 15, 2026
- High CVE-2026-83016 Improper Access Control in Oracle Peoplesoft Enterprise Peopletools Sep 15, 2026
- High CVE-2026-83015 Improper Access Control in Oracle Peoplesoft Enterprise Peopletools Sep 15, 2026
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2021-22947 is "When curl >= 7.20.0 and <= 7.78.0 connects to an IMAP or POP3 server to retrieve data using...", rated Medium. It affects Macos (Apple); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.9 describes technical severity. EPSS 3.01% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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