CVE Intelligence
Medium Cryptography exploit reference

CVE-2023-28321 — An improper certificate validation vulnerability exists in curl <v8.1.0 in the way it supports...

An improper certificate validation vulnerability exists in curl <v8.1.0 in the way it supports matching of wildcard patterns when listed as "Subject Alternative Name" in TLS server certificates. curl can be built to use its own name matching function for TLS rather than one provided by a TLS library. This private wildcard matching function would match IDN (International Domain Name) hosts incorrectly and could as a result accept patterns that otherwise should mismatch. IDN hostnames are converted to puny code before used for certificate checks. Puny coded names always start with `xn--` and should not be allowed to pattern match, but the wildcard check in curl could still check for `x*`, which would match even though the IDN name most likely contained nothing even resembling an `x`.

Published May 26, 2023 · Updated Oct 23, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: hackerone

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 1.8% (30-day exploitation probability)+12
  • 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.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
1.81%
ahead of 78% of scored CVEs · Oct 24, 2026
Affects
Apple
Macos and 9 more
CVSS base
5.9
Medium · 4 source(s)

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.

Exploitation
Proof of concept
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — hackerone.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.

  1. Identify exposed assets running the affected vendor/product/version combinations (Apple Macos, Debian Debian Linux, Fedoraproject Fedora…).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. Apply the fixed version or the patch documented under Remediation.
  4. Search available logs for exploit probes matching the vulnerability class (cryptography), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Apple Macos ≥ 11.0 and < 11.7.9≥ 12.0 and < 12.6.8≥ 13.0 and < 13.5 Vulnerable NIST National Vulnerability Database
Debian Debian Linux version 10.0 Vulnerable NIST National Vulnerability Database
Fedoraproject Fedora version 37version 38 Vulnerable NIST National Vulnerability Database
Haxx Curl < 8.1.0 Vulnerable NIST National Vulnerability Database
Netapp Clustered Data Ontap 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 H500s 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 Ontap Antivirus Connector versions not specified by the source Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored 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
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.

CWE-295 · Improper Certificate Validation

Other CVEs with this weakness →

EPSS over time FIRST

Oct 23, 2026 → Oct 24, 2026 · 2 reading(s) · max 1.81%

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).
  • Check TLS negotiations and unexpected certificates in the component’s traffic.
web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 23, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 23, 2026
  • Fix documented
    Oct 23, 2026 · NIST National Vulnerability Database
  • Affected products added · haxx/curl, debian/debian linux, fedoraproject/fedora, netapp/clustered data ontap, netapp/ontap antivirus connector, net
    Oct 23, 2026 · NIST National Vulnerability Database
  • CVSS changed · 5.9
    Oct 23, 2026 · NIST National Vulnerability Database
  • Source status changed · → Modified
    Oct 23, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 23, 2026 · Alertas do Telegram
  • 2023
  • CVE published
    May 26, 2023 · hackerone

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 23, 2026 – Oct 23, 2026
  • 1× Official description updated · Oct 23, 2026 – Oct 23, 2026

References

19 on the record

Elsewhere on this site

Apple
every CVE for this vendor
Cryptography
same class
CWE-295
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-86979 Exposure of Sensitive Information in Apple Macos 5d
  • CVE-2026-86975 Out-of-bounds Read in Apple iOS and iPadOS 5d
  • CVE-2026-86981 Out-of-bounds Write in Apple Macos 5d
  • CVE-2026-86976 Improper Authorization in Apple iOS and iPadOS 5d
  • CVE-2026-86957 An out-of-bounds read was addressed with improved bounds checking. This issue is fixed in iOS 26... 5d
  • CVE-2026-86953 Out-of-bounds Write in Apple iOS and iPadOS 5d

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-2023-28321 is "An improper certificate validation vulnerability exists in curl <v8.1.0 in the way it supports...", 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 1.81% 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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