CVE-2023-28321

Exp

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: 2023-05-26 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-28321 is rated High Exploit Risk (66.5/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.81%). 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +1.41% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2023-28321

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2023-28321

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.40% 1.81% +1.41%
2 2026-06-13 0.30% 0.40% +0.11%
3 2026-03-04 — 0.30% —

Full EPSS history (34 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-28321

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.9 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.2 3.6 [email protected]
5.9 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.2 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2023-28321

OS Trackers for CVE-2023-28321

vendor priority summary link
alpine — CVE-2023-28321: 1 source package rows (curl); 182 state rows across 7 repos (3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 7, open 175. https://security.alpinelinux.org/vuln/CVE-2023-28321
debian not yet assigned CVE-2023-28321 not yet assigned priority: Debian including 1 source packages (curl), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2023-28321
gentoo high CVE-2023-28321: 1 GLSA(s) (202310-12), 1 atom(s) (net-misc/curl); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2023-28321
redhat medium — https://access.redhat.com/security/cve/CVE-2023-28321
suse medium CVE-2023-28321 severity moderate: SUSE including 405 source package names (0.23.0.3.2.452:libcurl4-7.66.0-150200.4.57.1, 0.58.0.1.264:libcurl4-8.0.1-150400.5.23.1, …), 967 product×package rows across 322 product lines (Container bci/bci-init, Container bci/dotnet-aspnet, … (322 product lines)): Fixed 806, Known Affected 152, Known Not Affected 9. https://www.suse.com/security/cve/CVE-2023-28321/
ubuntu low CVE-2023-28321 low priority: Ubuntu including 1 source packages (curl), 13 status rows across 13 suites (bionic, focal, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): released 13. https://ubuntu.com/security/CVE-2023-28321

Affected software / configurations for CVE-2023-28321

Vendor Product Version Raw CPE
haxx curl < 8.1.0 cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
fedoraproject fedora 37 cpe:2.3:o:fedoraproject:fedora:37:*:*:*:*:*:*:*
fedoraproject fedora 38 cpe:2.3:o:fedoraproject:fedora:38:*:*:*:*:*:*:*
netapp clustered_data_ontap — cpe:2.3:a:netapp:clustered_data_ontap:-:*:*:*:*:*:*:*
netapp ontap_antivirus_connector — cpe:2.3:a:netapp:ontap_antivirus_connector:-:*:*:*:*:*:*:*
netapp h300s_firmware — cpe:2.3:o:netapp:h300s_firmware:-:*:*:*:*:*:*:*
netapp h500s_firmware — cpe:2.3:o:netapp:h500s_firmware:-:*:*:*:*:*:*:*
netapp h700s_firmware — cpe:2.3:o:netapp:h700s_firmware:-:*:*:*:*:*:*:*
netapp h410s_firmware — cpe:2.3:o:netapp:h410s_firmware:-:*:*:*:*:*:*:*
apple macos >= 11.0, < 11.7.9 cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*
apple macos >= 12.0, < 12.6.8 cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*
apple macos >= 13.0, < 13.5 cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*

References for CVE-2023-28321

URL Tags
http://seclists.org/fulldisclosure/2023/Jul/47 Mailing List Third Party Advisory
http://seclists.org/fulldisclosure/2023/Jul/48 Mailing List Third Party Advisory
http://seclists.org/fulldisclosure/2023/Jul/52 Mailing List Third Party Advisory
https://hackerone.com/reports/1950627 Exploit Patch Third Party Advisory
https://lists.debian.org/debian-lts-announce/2023/10/msg00016.html Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/F4I75RDGX5ULSSCBE5BF3P5I5SFO7ULQ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Z2LIWHWKOVH24COGGBCVOWDXXIUPKOMK/
https://security.gentoo.org/glsa/202310-12 Third Party Advisory
https://security.netapp.com/advisory/ntap-20230609-0009/ Third Party Advisory
https://support.apple.com/kb/HT213843 Third Party Advisory
https://support.apple.com/kb/HT213844 Third Party Advisory
https://support.apple.com/kb/HT213845 Third Party Advisory
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