What is the CVSS score of EUVD-2026-80888?

EUVD-2026-80888 has a CVSS 3.1 base score of 7.4 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N. EPSS exploitation probability: 0.2%.

How to fix or mitigate EUVD-2026-80888?

Within 24 hours, inventory every internal and vendor-supplied application, service, or pipeline that links sequoia-openpgp and processes OpenPGP certificates from untrusted sources, and confirm the exact library version in use; where such validation is non-essential, temporarily disable processing of externally supplied certificates or route key verification through a trusted, curated keyring instead of accepting arbitrary input. Within 7 days, for deployments that must continue validating third-party certificates, add a secondary verification layer outside Sequoia (for example, independent back-signature or fingerprint checks using an alternate PGP implementation) and reject legacy v4 certificates that omit the key-flags subpacket, which is the condition this flaw exploits; also open a tracked escalation with any third-party vendor whose product embeds sequoia-openpgp. Within 30 days, subscribe to the upstream Sequoia security advisory channel and the RustSec advisory database, plan an emergency change window to deploy the vendor-released patched sequoia-openpgp version as soon as it is published, and re-enable any validation paths disabled during triage once the fixed release is confirmed in production.

Sequoia OpenPGP EUVD-2026-80888

| CVE-2026-42784 HIGH

Improper Verification of Cryptographic Signature (CWE-347)

2026-09-16 secalert@redhat.com

GHSA-g33h-rrj9-75qv

Authentication Bypass Rust

7.4

CVSS 3.1 · Vendor: redhat

View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

Access

Craft certificate lacking key-flags subpacket
Delivery

Deliver certificate to victim application
Exploit

Library misinfers key flags
Execution

Back-signature check bypassed
Persist

Bind rogue subkey, forge signatures
Impact

Malicious signature accepted as valid

Vulnerability Assessment

Weakness	CWE CWE-347 OWASP Top 10:2025 A04:2025 - Cryptographic Failures ASVS 5.0 V11 - Cryptography Signature verification
Exploitation Conditions	Exploitation specifically requires an OpenPGP certificate that is missing a key-flags subpacket (the legacy/older-certificate code path); the library then incorrectly infers key flags, producing the key-flag confusion that bypasses the back-signature check and permits binding an arbitrary subkey. The victim system must actually process and verify the attacker-supplied certificate with sequoia-openpgp (UI:R), which is the main limiting factor - there is no default remote-service exposure. No authentication is required (PR:N). Any application relying on this library for OpenPGP signature verification is exposed once it ingests the crafted certificate.
Impact	This is a cryptographic signature-verification bypass (CWE-347) in the sequoia-openpgp library. The provided CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N, base 7.4) is internally coherent: no privileges required, low complexity, but user interaction is needed (a victim application/user must process the attacker-supplied certificate), and scope is changed because the library's flawed trust decision propagates to the relying application. Impact is integrity-only (I:H) - forged/illegitimately-bound signatures - with no confidentiality or availability impact, which matches the description. No EPSS score, no CISA KEV listing, and no public POC are present in the supplied data, so exploitation is: no public exploit identified at time of analysis. This is a genuine correctness/integrity flaw in a security-critical primitive (signature verification), so it is a real priority for any deployment that verifies OpenPGP certificates with this library, but the lack of active-exploitation or POC signals and the UI:R requirement mean it is not an urgent mass-exploitation threat. The 'Jwt Attack' tag is incorrect and misleading - this is OpenPGP, not JWT - and should not factor into triage.
Exploit ScenarioDerived	An attacker crafts a malicious OpenPGP certificate that lacks a key-flags subpacket (as older certificates do), causing sequoia-openpgp to infer key capabilities incorrectly and skip the back-signature check. The attacker binds an arbitrary subkey to their own certificate and presents it to a victim system that verifies signatures with the library, which then accepts forged signatures as valid. No public exploit code is identified at this time; exploitation requires the victim to process the attacker's certificate (UI:R).

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

No patch listed yet 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 16, 2026

Signature forgery in Sequoia OpenPGP (sequoia-openpgp) stems from incorrect key-flag inference for legacy OpenPGP certificates that lack a key-flags subpacket, letting an unauthenticated remote attacker bypass the back-signature check and bind an arbitrary subkey to their own certificate. This compromises cryptographic integrity for any application that uses the library to verify untrusted certificates, although exploitation requires the victim to process a crafted certificate (UI:R). No public exploit code or CISA KEV entry was identified in the provided data.

RemediationAI

No vendor-released patch was identified at time of analysis. Until a fix is available, applications should avoid verifying untrusted OpenPGP certificates with sequoia-openpgp; if that is not possible, add strict pre-validation that rejects any certificate lacking an explicit key-flags subpacket before processing, accepting that this may break interoperability with legitimate older certificates. Monitor the Red Hat advisory at https://access.redhat.com/security/cve/CVE-2026-42784 and the Bugzilla report at https://bugzilla.redhat.com/show_bug.cgi?id=2464122 for a patched version. A compensating control is to perform independent back-signature verification with a different OpenPGP implementation before trusting a subkey binding, though this adds complexity and potential performance overhead.

Affected ProductsAI

The affected product is the sequoia-openpgp library used to parse and verify OpenPGP certificates. No CPE strings or exact version ranges were supplied in the available intelligence; Red Hat tracks the issue at https://access.redhat.com/security/cve/CVE-2026-42784 and a bug report exists at https://bugzilla.redhat.com/show_bug.cgi?id=2464122. Applications that embed sequoia-openpgp for certificate validation, including those that process certificates missing a key-flags subpacket, are exposed.

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Technical ContextAI · show details

OpenPGP certificates use key flags subpackets within self-signatures to declare capabilities such as certify, sign, encrypt, or authenticate, and a back-signature (subkey binding signature) cryptographically ties each subkey to the primary key. CVE-2026-42784 is a CWE-347 improper verification of cryptographic signature flaw in sequoia-openpgp: when an older certificate omits the key-flags subpacket, the library incorrectly infers key flags instead of safely rejecting or handling the absence. This inference discrepancy causes the back-signature check to be bypassed, so an attacker can illegitimately bind an arbitrary subkey to their own certificate and forge signatures. The root cause is in the certificate verification path that handles legacy certificates, and any application that relies on sequoia-openpgp for OpenPGP signature verification is exposed once it ingests such a crafted certificate.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (redhat) PRIMARY 7.4 HIGH

AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N

vuln.today AI 7.4 HIGH

Certificate is network-delivered (AV:N) and unauthenticated (PR:N) but must be processed by the victim (UI:R); flawed verification propagates to the relying application (S:C) with integrity-only impact (I:H, C:N/A:N).

3.1 AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N

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

SUSE 6.5 MEDIUM

AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Red Hat 7.4 HIGH

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

None

Integrity

High

Availability

None

DescriptionCVE.org

A flaw was found in sequoia-openpgp. The library incorrectly infers key flags for older certificates when a key flags subpacket is missing, leading to a discrepancy in how key capabilities are viewed. This key flag confusion allows an attacker to bypass the back-signature check. Consequently, an attacker can illegitimately bind an arbitrary subkey to their own certificate and forge signatures, completely compromising cryptographic integrity.

Executive ViewAI

Why It Matters

A HIGH-severity signature-forgery flaw in the Sequoia OpenPGP library (sequoia-openpgp) lets a crafted certificate bypass the back-signature check and bind an attacker-controlled subkey to a legitimate certificate, undermining the cryptographic trust decisions made by any application that validates untrusted OpenPGP keys. Because Sequoia is a widely embedded library, exposure may extend well beyond teams that deploy it directly into third-party products and internal tooling. No vendor patch is available at this time, so leadership should treat this as an unmitigated integrity risk requiring immediate inventory and interim verification controls.

Business Impact: High

Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations: disable or sandbox verification of untrusted OpenPGP certificates where business processes allow; enforce a strict allowlist of trusted keys and fingerprints rather than accepting arbitrary certificates; reject legacy OpenPGP certificates that lack a key-flags subpacket; add an independent back-signature/fingerprint validation step using a separate PGP implementation; and monitor the upstream Sequoia advisory channel for the eventual patched release and deploy it on an expedited timeline.

Threat Intelligence Overview

EPSS Score

0.2%

Top 95% exploitable

Prevalence

Medium

Popular Rust OpenPGP library (sq, Debian tooling), but not universally deployed

Data Quality

6 sources

Confidence: High

EUVD

NVD

CVE.org

EPSS MSRC Vendor

VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC No

EPSS 0.2%

Patch available No

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Human Impact

High

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +37

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Authentication Bypass CRITICAL

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

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Vendor StatusVendor

SUSE

Severity: Moderate

Product	Status
SUSE Linux Enterprise Desktop 15 SP7	Not-Affected
SUSE Linux Enterprise Module for Development Tools 15 SP7	Not-Affected
SUSE Linux Enterprise Server 15 SP7	Not-Affected
SUSE Linux Enterprise Server 16.0	Not-Affected
SUSE Linux Enterprise Server 16.1	Not-Affected

References

Advisories & patches

Search Externally

GitHub PoC

Exploit-DB PacketStorm Snyk Rapid7 Nuclei Templates Trickest PoC

Back

SUSE Linux Enterprise Server for SAP Applications 15 SP7	Not-Affected
SUSE Linux Enterprise Server for SAP applications 16.0	Not-Affected
SUSE Linux Enterprise Server for SAP applications 16.1	Not-Affected
openSUSE Leap 16.0	Not-Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS	Not-Affected
SUSE Linux Enterprise High Performance Computing 15 SP5	Not-Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS	Not-Affected
SUSE Linux Enterprise Module for Development Tools 15 SP4	Not-Affected
SUSE Linux Enterprise Module for Development Tools 15 SP5	Not-Affected
SUSE Linux Enterprise Module for Development Tools 15 SP6	Not-Affected
SUSE Linux Enterprise Server 15 SP4	Not-Affected
SUSE Linux Enterprise Server 15 SP4-LTSS	Not-Affected
SUSE Linux Enterprise Server 15 SP5	Not-Affected
SUSE Linux Enterprise Server 15 SP5-LTSS	Not-Affected
SUSE Linux Enterprise Server 15 SP6	Not-Affected
SUSE Linux Enterprise Server 15 SP6-LTSS	Not-Affected
SUSE Linux Enterprise Server for SAP Applications 15 SP4	Not-Affected
SUSE Linux Enterprise Server for SAP Applications 15 SP5	Not-Affected
SUSE Linux Enterprise Server for SAP Applications 15 SP6	Not-Affected
SUSE Enterprise Storage 7.1	Affected
SUSE Linux Enterprise Desktop 15 SP3	Affected
SUSE Linux Enterprise Desktop 15 SP4	Not-Affected
SUSE Linux Enterprise Desktop 15 SP5	Not-Affected
SUSE Linux Enterprise Desktop 15 SP6	Not-Affected
SUSE Linux Enterprise High Performance Computing 15 SP3	Affected
SUSE Linux Enterprise High Performance Computing 15 SP3-ESPOS	Affected
SUSE Linux Enterprise High Performance Computing 15 SP3-LTSS	Affected
SUSE Linux Enterprise High Performance Computing 15 SP4	Not-Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS	Not-Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS	Not-Affected
SUSE Linux Enterprise Module for Development Tools 15 SP3	Affected
SUSE Linux Enterprise Real Time 15 SP3	Affected
SUSE Linux Enterprise Real Time 15 SP4	Not-Affected
SUSE Linux Enterprise Server 15 SP3	Affected
SUSE Linux Enterprise Server 15 SP3-BCL	Affected
SUSE Linux Enterprise Server 15 SP3-LTSS	Affected
SUSE Linux Enterprise Server for SAP Applications 15 SP3	Affected
SUSE Manager Proxy 4.2	Affected
SUSE Manager Proxy 4.3	Not-Affected
SUSE Manager Retail Branch Server 4.2	Affected
SUSE Manager Retail Branch Server 4.3	Not-Affected
SUSE Manager Server 4.2	Affected
SUSE Manager Server 4.3	Not-Affected
openSUSE Leap 15.3	Affected
openSUSE Leap 15.4	Not-Affected
openSUSE Leap 15.5	Not-Affected
openSUSE Leap 15.6	Not-Affected