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NVD / CVE Program· CNA EEF

CVE-2026-42791: OCSP responder certificate validity period not checked in public_key

Noroxi assessment

Priority: Monitor (action score 25/100)

  • 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: 0.31% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: Erlang OTP 1.17.1.3, 1.20.3.1, 1.21.1.

Low priority for now. Upgrade to Erlang OTP 1.17.1.3, 1.20.3.1, 1.21.1 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_ocsp module) allows forged OCSP responses signed with an expired responder certificate to be accepted as valid. OCSP response verification in pubkey_ocsp:verify_response/5 and pubkey_ocsp:is_authorized_responder/3 in lib/public_key/src/pubkey_ocsp.erl does not check the validity period (notBefore/notAfter) of the OCSP responder certificate. An attacker who has obtained the private key of an expired CA-designated OCSP responder certificate can forge OCSP responses that Erlang/OTP accepts as valid. This affects TLS clients using OCSP stapling via the ssl application: a malicious or compromised server can present a revoked TLS certificate together with a forged OCSP response signed by an expired responder key, and the client will accept the revoked certificate as valid. It also affects applications calling public_key:pkix_ocsp_validate/5 directly, where the impact depends on the use case — server-side client certificate validation using this API may allow authentication bypass with a revoked client certificate. This issue affects OTP from OTP 27.0 before OTP 29.0.1, OTP 28.5.0.1 and OTP 27.3.4.12, corresponding to public_key from 1.16 before 1.21.1, 1.20.3.1 and 1.17.1.3.

MediumCVSS 6.3 · v4.0—No exploit Fix available
Published
May 27, 2026
Updated
Oct 26, 2026
EPSS
0.3% · 24th percentile

Report tools

JSON

Action score

25

Monitor

Low priority for now.

CVSS
25 / 40 · 6.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · EEF
6.3
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:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N

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

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
erlangerlang/otp

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Affected versions

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

  • 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

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

    • 1.16 and lateraffected · otpfixed in 1.17.1.3, 1.20.3.1, 1.21.1
    • 27.0 and lateraffected · otpfixed in 27.3.4.12, 28.5.0.1, 29.0.1
    • 2b1a742c651b90f8a7a1fb2ddde73f29915ea376 and lateraffected · gitfixed in 7995f1fdaee3da569bb810358ce0f546471d169b, b3870e02405c709a872b01ba6086065620cdfe76

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:13erlangbefore 1:27.3.4.1+dfsg-1+deb13u31:27.3.4.1+dfsg-1+deb13u3
Debian:14erlangbefore 1:27.3.4.12+dfsg-11:27.3.4.12+dfsg-1
openSUSE:Leap 16.0erlangbefore 27.1.3-160000.5.127.1.3-160000.5.1
openSUSE:Tumbleweederlangbefore 28.5.0.4-1.128.5.0.4-1.1
openSUSE:Tumbleweederlang27before 27.1.3-2.127.1.3-2.1
Red Hat:hummingbird:1erlang27before 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-asn1before 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-common_testbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-compilerbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-cryptobefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-debuggerbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-dialyzerbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-diameterbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-edocbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-eldapbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-erl_interfacebefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-ertsbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-etbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-eunitbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-examplesbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-ftpbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-gdb-toolsbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-inetsbefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1
Red Hat:hummingbird:1erlang27-jinterfacebefore 0:27.3.4.17-1.hum10:27.3.4.17-1.hum1

+21

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-2026-32147Apr 21, 2026 · SFTP chroot bypass via path traversal in SSH_FXP_FSETSTAT
    21Monitor
  • ← EarlierCVE-2026-42789May 27, 2026 · Non-CA certificate accepted as intermediate issuer in public_key path validation
    28Monitor
  • Later →CVE-2026-42790May 27, 2026 · nameConstraints DNS bypass via subject CommonName fallback in public_key hostname verification
    30Monitor

Remediation

Which version to upgrade to

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

Product / packageFixed versionSource
Erlang OTP1.17.1.3Vendor (CNA)
Erlang OTP1.20.3.1Vendor (CNA)
Erlang OTP1.21.1Vendor (CNA)
Erlang OTP27.3.4.12Vendor (CNA)
Erlang OTP28.5.0.1Vendor (CNA)
Erlang OTP29.0.1Vendor (CNA)
Erlang OTP7995f1fdaee3da569bb810358ce0f546471d169bVendor (CNA)
Erlang OTPb3870e02405c709a872b01ba6086065620cdfe76Vendor (CNA)
debian:erlang1:27.3.4.1+dfsg-1+deb13u3 · Debian:13Package registry (OSV)
opensuse:erlang28.5.0.4-1.1 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:erlang2727.1.3-2.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:erlang270:27.3.4.17-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-asn10:27.3.4.17-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-common_test0:27.3.4.17-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-compiler0:27.3.4.17-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-crypto0:27.3.4.17-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-debugger0:27.3.4.17-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-dialyzer0:27.3.4.17-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-diameter0:27.3.4.17-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-edoc0:27.3.4.17-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-eldap0:27.3.4.17-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-erl_interface0:27.3.4.17-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-erts0:27.3.4.17-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
suse:erlang27.1.3-160000.5.1 · SUSE:Linux Enterprise Server 16.0Package 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.

No history yet (it accumulates with the daily EPSS job).

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.

Variant candidates

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

  • CVE-2026-427900 days apartnameConstraints DNS bypass via subject CommonName fallback in public_key hostname verification
    30Monitor
  • 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

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action 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
None
Scope
X

Weakness class (CWE)

CWE-295 · Improper Certificate Validation

CVSS vector

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/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
override fun checkServerTrusted(chain: Array<X509Certificate>, type: String) {  // Left empty for the test environment}

Fixed

kotlin
val client = OkHttpClient.Builder()  .certificatePinner(    CertificatePinner.Builder()      .add("api.sirius.example", "sha256/…")      .build()  ).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.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

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

References

Show all references (5 more)

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

All records