GHSA-jhm7-29pj-4xvf — @node-oauth/oauth2-server
MEDIUMGHSA-jhm7-29pj-4xvf is a medium-severity (CVSS 5.9) CWE-307 vulnerability in @node-oauth/oauth2-server. A fix is available for @node-oauth/oauth2-server — see the affected versions and patch details below.
@node-oauth/oauth2-server: PKCE code_verifier ABNF not enforced in token exchange allows brute-force redemption of intercepted authorization codes
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 GHSA-jhm7-29pj-4xvf.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-jhm7-29pj-4xvf plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@node-oauth/oauth2-servernpmDescription
Summary
The token exchange path accepts RFC7636-invalid code_verifier values (including one-character strings) for S256 PKCE flows.
Because short/weak verifiers are accepted and failed verifier attempts do not consume the authorization code, an attacker who intercepts an authorization code can brute-force code_verifier guesses online until token issuance succeeds.
Root cause
lib/pkce/pkce.js(getHashForCodeChallenge) only checks thatverifieris a non-empty string before hashing forS256; it does not enforce RFC7636 ABNF (43..128unreserved chars).lib/grant-types/authorization-code-grant-type.jscompareshash(code_verifier)to storedcodeChallengewithout validating verifier format/length.- In
AuthorizationCodeGrantType.handle, authorization code revocation happens after verifier validation. Invalid guesses fail before revoke, so the same code can be retried repeatedly.
Steps to Reproduce
Setup
- PKCE authorization code exists with:
codeChallengeMethod = "S256"codeChallenge = BASE64URL(SHA256("z"))(verifier is one character, RFC-invalid)
- Attacker has intercepted the authorization code value.
Reproduction
- Send repeated token requests with guessed
code_verifiervalues:
POST /token HTTP/1.1
Host: oauth.example
Content-Type: application/x-www-form-urlencoded
grant_type=authorization_code&
client_id=client1&
client_secret=s3cret&
code=stolen-auth-code&
redirect_uri=https://client.example/callback&
code_verifier=<guess>
- Observe invalid guesses return
invalid_grant. - Continue guessing (
a..z). - When
code_verifier=z, token issuance succeeds and returns bearer tokens.
Confirmed PoC output
BRUTE_FORCE_SUCCESS { tries: 26, guess: 'z', status: 200, tokenIssued: true }
Impact
An intercepted authorization code can be redeemed by brute-forcing low-entropy verifiers that the server should have rejected under RFC7636.
This weakens PKCE’s protection goal and allows token theft when clients generate short/predictable verifiers.
Recommended Fix
- Enforce
pkce.codeChallengeMatchesABNF(request.body.code_verifier)in authorization code token exchange before hashing/comparison. - Reject verifier values outside RFC7636 charset/length (
43..128unreserved). - Invalidate authorization codes on failed verifier attempts (or add strict retry limits) to prevent online guessing.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @node-oauth/oauth2-server | all versions | 5.3.0npm install @node-oauth/oauth2-server@5.3.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @node-oauth/oauth2-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @node-oauth/oauth2-server to 5.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jhm7-29pj-4xvf is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-jhm7-29pj-4xvf can be triaged on real exposure rather than presence alone.
Tailored to GHSA-jhm7-29pj-4xvf. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-jhm7-29pj-4xvf in your dependencies?
O3 Security finds GHSA-jhm7-29pj-4xvf across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.