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CVE-2026-49264 medium CVSS 6.1

Cross-Site Scripting (XSS) in oauthlib (CVE-2026-49264)

Summary

Cross-site scripting in oauthlib (CVE-2026-49264). Risk of unauthorized operations or information disclosure. Exploitable via POST /revoke. Mitigation: upgrade to 4.0.0 or later.

Original description

The description as published by the source.

Summary

When enable_jsonp=True, oauthlib's RevocationEndpoint reflects the user-supplied callback parameter directly into JavaScript response bodies on both success and error paths without validating that it is a legal JSONP callback name. This allows arbitrary JavaScript response generation instead of a restricted function call, making the documented JSONP revocation feature unsafe for browser-based JSONP consumption when attackers can influence callback.

Details

The issue is in oauthlib/oauth2/rfc6749/endpoints/revocation.py.

When enable_jsonp=True is passed to the RevocationEndpoint constructor, two code paths wrap the response body using the user-supplied request.callback parameter:

# Error response path (line 72-73):
if self.enable_jsonp and request.callback:
    response_body = '{}({});'.format(request.callback, response_body)

# Success response path (line 81-82):
if self.enable_jsonp and request.callback:
    response_body = request.callback + '();'

The request.callback value comes from HTTP request parameters, either the query string or POST body, via the Request class in oauthlib/common.py (lines 394-395), which merges query and body parameters into _params. Any value the client sends as callback is used verbatim.

There is no validation of any kind on the callback parameter:

  • No check that it is a valid JavaScript identifier
  • No whitelist of allowed characters
  • No escaping or sanitization

A safe JSONP implem…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-49264 has been found in oauthlib.
Attackers can target a specific entry point like POST /revoke over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 6.1/10.
What to do: upgrade oauthlib to 4.0.0 or later.
If unsure, ask your IT team or search "oauthlib CVE-2026-49264" on the vendor's site.

CVE-2026-49264 (oauthlib) — CWE-79 / CVSS v3 6.1
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: POST /revoke / RevocationEndpoint / callback / request.callback
Patched: 4.0.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Cross-site scripting (XSS) (CWE-79) exists in oauthlib. Attackers reach the vulnerable code path via POST /revoke without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of oauthlib. Attack surface: POST /revoke / RevocationEndpoint / callback / request.callback.

🔥 Severity

Severity: Medium (CVSS 6.1/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 4.0.0.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual POST /revoke requests with malformed payloads or SQL meta-characters. Run grep -r 'oauthlib' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'oauthlib' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で oauthlib を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Hunt for indicators of compromise detect 
    grep 'POST /revoke' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで POST /revoke への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。

  3. 3
    Apply patch patch 
    Upgrade oauthlib to 4.0.0

    ステージング環境で 4.0.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。

  4. 4
    Post-deployment verification verify 
    Replay attack against POST /revoke on staging to confirm patch closes the vector

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。

Affected packages

pip oauthlib
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.0.0"}]}]
PyPI oauthlib
[{"type":"ECOSYSTEM","events":[{"introduced":"0.6.1"},{"fixed":"4.0.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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