NVD / CVE Program· CNA EEF

CVE-2026-42790: nameConstraints DNS bypass via subject CommonName fallback in public_key hostname verification

HighCVSS 7.6 · v4.0—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 30/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.35% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. Special conditions such as timing or configuration are required.
Fixed version: Erlang OTP 0769050c69d73762672b0db1347b6993a5b31759, 1.15.1.7, 1.17.1.3; azl3 erlang 26.2.5.20-1 on Azure Linux 3.0 26.2.5.21-1.

Low priority for now. Upgrade to Erlang OTP 0769050c69d73762672b0db1347b6993a5b31759, 1.15.1.7, 1.17.1.3; azl3 erlang 26.2.5.20-1 on Azure Linux 3.0 26.2.5.21-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_cert and public_key modules) allows a DNS nameConstraints bypass via subject CommonName fallback in TLS hostname verification. Two flaws combine to allow a subordinate CA whose DNS nameConstraints are restricted (e.g. permitted;DNS:allowed.example.com) to issue a leaf certificate that an OTP TLS client accepts as a valid identity for an out-of-scope hostname (e.g. victim.example.com): First, pubkey_cert:validate_names/6 in lib/public_key/src/pubkey_cert.erl only checks SAN DNS entries against nameConstraints. Per RFC 5280, a permitted DNS subtree only restricts certificates that contain a DNS-typed name. A leaf with no subjectAltName therefore trivially satisfies any permitted;DNS:... constraint regardless of its subject commonName. Second, public_key:pkix_verify_hostname/3 in lib/public_key/src/public_key.erl falls back to the subject commonName when no subjectAltName is present, extracting id-at-commonName attributes as presented IDs and matching them against the reference hostname. The strict pkix_verify_hostname_match_fun(https) matcher does not suppress this fallback. The result is that path validation accepts a CN-only leaf under a DNS-constrained intermediate (no SAN means the nameConstraints are not triggered), and hostname verification then accepts it via the CN fallback. The bypass is reachable from stock ssl:connect with verify_peer, a trusted CA, SNI, and the canonical strict https hostname matcher. This issue affects OTP from OTP 19.3 before OTP 26.2.5.21, OTP 27.3.4.12, OTP 28.5.0.1, and OTP 29.0.1, corresponding to public_key from 1.4 before 1.15.1.7, 1.17.1.3, 1.20.3.1, and 1.21.1.

Published: May 27, 2026
Updated: Nov 11, 2026
EPSS: 0.3% · 30th percentile
CWE: CWE-295

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.6 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.3%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · EEF: 7.6; NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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Not in KEV: no record of exploitation in the wild
No public exploit code on record
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Noroxi analysis

What does it mean in your environment?

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Affected systems

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Vendor	Product	CPE
erlang	erlang/otp	cpe:2.3:a:erlang:erlang/otp

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (EEF). Independent of NVD's CPE analysis and usually ahead of it.

Erlang OTP
- 19.3 and lateraffected · otpfixed in 26.2.5.21, 27.3.4.12, 28.5.0.1, 29.0.1
- 1.4 and lateraffected · otpfixed in 1.15.1.7, 1.17.1.3, 1.20.3.1, 1.21.1
- b0c245e8132bb13171e277b1af59c0cec00c9459 and lateraffected · gitfixed in 0769050c69d73762672b0db1347b6993a5b31759, fb67c6d1836f51105a96d8b769e71e4215a79457, 21abed64eb2026b5f82f432709e4e932f9be389a

Affected versions · NVD (4)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

erlang erlang/otp19.3 and later · before 26.2.5.21
erlang erlang/otp27.0 and later · before 27.3.4.12
erlang erlang/otp28.0 and later · before 28.5.0.1
erlang erlang/otp29.0 and later · before 29.0.1

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	erlang	from 0	—
Debian:13	erlang	before 1:27.3.4.1+dfsg-1+deb13u3	1:27.3.4.1+dfsg-1+deb13u3
Debian:14	erlang	before 1:27.3.4.12+dfsg-1	1:27.3.4.12+dfsg-1
openSUSE:Leap 16.0	erlang	before 27.1.3-160000.5.1	27.1.3-160000.5.1
openSUSE:Tumbleweed	erlang	before 28.5.0.4-1.1	28.5.0.4-1.1
openSUSE:Tumbleweed	erlang27	before 27.1.3-2.1	27.1.3-2.1
Red Hat:hummingbird:1	erlang27	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-asn1	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-common_test	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-compiler	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-crypto	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-debugger	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-dialyzer	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-diameter	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-edoc	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-eldap	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-erl_interface	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-erts	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-et	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-eunit	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-examples	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-ftp	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-gdb-tools	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1
Red Hat:hummingbird:1	erlang27-inets	before 0:27.3.4.17-1.hum1	0:27.3.4.17-1.hum1

+54

Same product

erlang: all records

Other highest-scoring records for the same primary product.

CVE-2026-55953TLS 1.2 and DTLS client accepts unoffered anonymous cipher suite, bypassing server authentication
36Monitor
CVE-2026-49759Stack buffer overflow in SCTP error cause parsing in inet_drv allows remote VM crash
35Monitor
CVE-2026-59251Denial of service via exponential certificate policy tree growth in path validation
34Monitor

Published before and after this one in the same product

← EarlierCVE-2026-42789May 27, 2026 · Non-CA certificate accepted as intermediate issuer in public_key path validation
28Monitor
← EarlierCVE-2026-42791May 27, 2026 · OCSP responder certificate validity period not checked in public_key
25Monitor
Later →CVE-2026-48855Jun 10, 2026 · SFTP READLINK Leaks Absolute Backend Filesystem Path When Root Is Configured
9Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Erlang OTP	0769050c69d73762672b0db1347b6993a5b31759	Vendor (CNA)
Erlang OTP	1.15.1.7	Vendor (CNA)
Erlang OTP	1.17.1.3	Vendor (CNA)
Erlang OTP	1.20.3.1	Vendor (CNA)
Erlang OTP	1.21.1	Vendor (CNA)
Erlang OTP	21abed64eb2026b5f82f432709e4e932f9be389a	Vendor (CNA)
Erlang OTP	26.2.5.21	Vendor (CNA)
Erlang OTP	27.3.4.12	Vendor (CNA)
Erlang OTP	28.5.0.1	Vendor (CNA)
Erlang OTP	29.0.1	Vendor (CNA)
Erlang OTP	fb67c6d1836f51105a96d8b769e71e4215a79457	Vendor (CNA)
azl3 erlang 26.2.5.20-1 on Azure Linux 3.0	26.2.5.21-1 · CBL-Mariner Releases	Microsoft (MSRC)
debian:erlang	1:27.3.4.1+dfsg-1+deb13u3 · Debian:13	Package registry (OSV)
opensuse:erlang	28.5.0.4-1.1 · openSUSE:Tumbleweed	Package registry (OSV)
opensuse:erlang27	27.1.3-2.1 · openSUSE:Tumbleweed	Package registry (OSV)
red hat:erlang	0:26.2.5.21-2.el9ost · Red Hat:openstack:18.0::el9	Package registry (OSV)
red hat:erlang-asn1	0:26.2.5.21-2.el9ost · Red Hat:openstack:18.0::el9	Package registry (OSV)
red hat:erlang-asn1-debuginfo	0:26.2.5.21-2.el9ost · Red Hat:openstack:18.0::el9	Package registry (OSV)
red hat:erlang-compiler	0:26.2.5.21-2.el9ost · Red Hat:openstack:18.0::el9	Package registry (OSV)
red hat:erlang-crypto	0:26.2.5.21-2.el9ost · Red Hat:openstack:18.0::el9	Package registry (OSV)
red hat:erlang-crypto-debuginfo	0:26.2.5.21-2.el9ost · Red Hat:openstack:18.0::el9	Package registry (OSV)
red hat:erlang-debuginfo	0:26.2.5.21-2.el9ost · Red Hat:openstack:18.0::el9	Package registry (OSV)
red hat:erlang-debugsource	0:26.2.5.21-2.el9ost · Red Hat:openstack:18.0::el9	Package registry (OSV)
red hat:erlang-eldap	0:26.2.5.21-2.el9ost · Red Hat:openstack:18.0::el9	Package registry (OSV)
red hat:erlang-erl_interface-debuginfo	0:26.2.5.21-2.el9ost · Red Hat:openstack:18.0::el9	Package registry (OSV)
red hat:erlang-erts	0:26.2.5.21-2.el9ost · Red Hat:openstack:18.0::el9	Package registry (OSV)
red hat:erlang-erts-debuginfo	0:26.2.5.21-2.el9ost · Red Hat:openstack:18.0::el9	Package registry (OSV)
suse:erlang	27.1.3-160000.5.1 · SUSE:Linux Enterprise Server 16.0	Package registry (OSV)
suse:erlang26	26.2.1-150300.7.28.1 · SUSE:Linux Enterprise Module for Server Applications 15 SP7	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

John Downeyfinder
Ingela Anderton Andinremediation developer
Dan Gudmundssonremediation reviewer
Jakub Witczakremediation reviewer

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-3214450 days apartOCSP designated-responder authorization bypass via missing signature verification
30Monitor
CVE-2026-427890 days apartNon-CA certificate accepted as intermediate issuer in public_key path validation
28Monitor
CVE-2026-427910 days apartOCSP responder certificate validity period not checked in public_key
25Monitor

Not on record for this CVE: EPSS history · public bounty program.

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
Special conditions such as timing or configuration are required.

If successful

Confidentiality
Integrity
Availability

Attack vector: Network
Attack complexity: High
Privileges required: None
User interaction: P
Scope: X

Weakness class (CWE)

CWE-295 · Improper Certificate Validation

CVSS vector

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Root cause

A certificate validation error is silently swallowed instead of terminating the connection. Often, code added for a test environment makes its way into production.

The bug in code

The whole CWE-295 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

kotlin

1override fun checkServerTrusted(chain: Array<X509Certificate>, type: String) {
2  // Left empty for the test environment
3}

Fixed

kotlin

1val client = OkHttpClient.Builder()
2  .certificatePinner(
3    CertificatePinner.Builder()
4      .add("api.sirius.example", "sha256/…")
5      .build()
6  ).build()

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

—

Change log (1)

Fix✗ → ✓Sep 28, 2026, 10:11 PM UTC

For records you follow, these changes also arrive as notifications. →

References

cna.erlef.org/cves/CVE-2026-42790.html

Show all references (12 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records