Go JOSE: DoS when parsing JWKs that contain RSA keys

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-116587: 0.37% estimated exploitation activity in the next 30 days; percentile 30.52 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A crafted RSA key inside a JWK can cause operations that parse JWKs to consume excess CPU.

Details go-jose does not check for bounds on RSA modulus and primes before validating them. Values are passed directly to `crypto/rsa.PrivateKey.Validate()`. On Go 1.24+, this takes cubic time complexity with respect to the RSA modulus and primes. This allows an attacker to supply a crafted JWK to consume excessive CPU. https://github.com/go-jose/go-jose/blob/5b371aecfcf7aabe06068d67da4344591ecddc76/jwk.go#L655-L700

Proof of concept No special configuration of go-jose is required to reproduce this vulnerability. ```go 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 :=…

Published by the source

27 Oct 2026, 19:01 UTC

Last modified by the source

27 Oct 2026, 19:15 UTC

Source last checked

28 Oct 2026, 06:30 UTC

1. Revision 2 · amended · 28 Oct 2026

   Amended from osv record GHSA-mgcc-cww5-fp2q

2. Revision 1 · created · 27 Oct 2026

   Published from ghsa record GHSA-mgcc-cww5-fp2q

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-116587

Advisory: Go JOSE: DoS when parsing JWKs that contain RSA keys
IDs: CVE-2026-116587, GHSA-mgcc-cww5-fp2q
Record: https://patchnext.com/advisories/cve-2026-116587 (revision 2, source checked 28 Oct 2026, 06:30 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/go-jose/go-jose/v4 4.1.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/go-jose/go-jose/v3: affected <= 3.0.5
- Go github.com/go-jose/go-jose/v4: affected < 4.1.6; fixed in 4.1.6

## Suggested inspection (read-only)
- Go github.com/go-jose/go-jose/v3: check the installed version with your package manager.
- Go github.com/go-jose/go-jose/v4: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/go-jose/go-jose/v3, github.com/go-jose/go-jose/v4.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-mgcc-cww5-fp2q (GitHub-reviewed advisory GHSA-mgcc-cww5-fp2q lists affected ranges: Go github.com/go-jose/go-jose/v4 >=0 =0 <=3.0.5)
- Verified: https://osv.dev/vulnerability/GHSA-mgcc-cww5-fp2q (OSV record GHSA-mgcc-cww5-fp2q lists affected ranges: Go github.com/go-jose/go-jose/v4 >=0 =0 <=3.0.5)

Commands are suggestions: review each one before running it.