CVE-2021-22945 — When sending data to an MQTT server, libcurl <= 7.73.0 and 7.78.0 could in some circumstances...
When sending data to an MQTT server, libcurl <= 7.73.0 and 7.78.0 could in some circumstances erroneously keep a pointer to an already freed memory area and both use that again in a subsequent call to send data and also free it *again*.
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 6.7% (30-day exploitation probability)+14
- Technical severity (critical)+10
- Automatable exploitation (SSVC)+3
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 — hackerone.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.
- EPSS ahead of 94% of scored CVEs: prioritize it in the patch queue.
- Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Apple | Macos | ≥ 12.0.0 and < 12.3 | Vulnerable | NIST National Vulnerability Database |
| Debian | Debian Linux | version 11.0 | Vulnerable | NIST National Vulnerability Database |
| Fedoraproject | Fedora | version 35version 33 | Vulnerable | NIST National Vulnerability Database |
| Haxx | Libcurl | ≥ 7.73.0 and ≤ 7.78.0 | 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 | Mysql Server | ≥ 5.7.0 and ≤ 5.7.35≥ 8.0.0 and ≤ 8.0.26 | Vulnerable | NIST National Vulnerability Database |
| Siemens | Sinec Ins | < 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 |
|---|---|---|---|---|---|
| 9.1 | CVSS 3.1 | Critical | 3.9 | 5.2 | nvd@nist.gov via NIST National Vulnerability Database |
| 9.1 | CVSS 3.1 | Critical | 3.9 | 5.2 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database |
| 9.1 | CVSS 3.1 | Critical | — | — | GitHub, Inc. via GitHub Security Advisories |
| 9.1 | CVSS 3.1 | Critical | — | — | CISA-ADP via CVE Program (cve.org) e CISA ADP |
| 5.8 | CVSS 2.0 | Medium | 8.6 | 4.9 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H (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 6.68%
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).
- Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
Timeline
What happened to this CVE, newest first.
- 2026
- SSVC assessment updated
- Record published
- Fix documented
- Affected products added · haxx/libcurl, fedoraproject/fedora, netapp/cloud backup, netapp/clustered data ontap, oracle/mysql server, netapp/h300s
- CVSS changed · 9.1
- 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
19 on the record
- hackerone.com/reports/1269242
- www.oracle.com/security-alerts/cpuoct2021.html
- cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/APOAK4
- www.debian.org/security/2022/dsa-5197
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/APOA
- nvd.nist.gov/vuln/detail/CVE-2021-22945
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RWLE
- support.apple.com/kb/HT213183
- 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
- github.com/advisories/GHSA-22mx-9r92-42g8
- cert-portal.siemens.com/productcert/html/ssa-398330.html
- cert-portal.siemens.com/productcert/html/ssa-389290.html
- 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
- 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
- Medium CVE-2026-64705 Classic Buffer Overflow in Apple Macos Aug 25, 2026
- High CVE-2026-43670 A Content Security Policy bypass was addressed with improved enforcement in AudioWorklet… Aug 25, 2026
- Medium CVE-2026-20679 Out-of-bounds Read in Apple Macos Aug 20, 2026
- High CVE-2026-65346 Integer Overflow or Wraparound in Apple Ipados Aug 17, 2026
- Medium CVE-2026-65341 Buffer Errors (Improper Restriction of Operations within Memory Bounds) in Apple Safari Aug 17, 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-2021-22945 is "When sending data to an MQTT server, libcurl <= 7.73.0 and 7.78.0 could in some circumstances...", rated Critical. It affects Macos (Apple); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.1 describes technical severity. EPSS 6.68% 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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