Affected: Homebrew: ansible

## Summary

A timing side-channel vulnerability exists in the PKCE (RFC 7636) implementation of the Authorization Code Grant flow. The `code_challenge_method_plain` function uses Python's standard `==` operator for string comparison instead of a constant-time comparison function, potentially allowing timing-based attacks.

## Affected Component

- File: `oauthlib/oauth2/rfc6749/grant_types/authorization_code.py` - Functions: `code_challenge_method_plain`, `code_challenge_method_s256` - Vulnerability Type: CWE-208 (Observable Timing Discrepancy)

## Technical Details

Python's `==` operator uses short-circuit evaluation when comparing strings: 1. Returns `False` immediately if lengths differ 2. Compares characters left-to-right, stopping at first mismatch

This means comparison time varies linearly with the length of the common prefix between the attacker-supplied verifier and the stored challenge, creating a measurable timing oracle.

## Proof of Concept

Tested locally against oauthlib source (network jitter eliminated to isolate pure Python execution time):

| Input | Result | Time (10M iterations) | |---|---|---| | Wrong first char (`B` + `A`*49) | Fast reject | 0.34106s | | 49 chars correct (`A`*49 + `B`) | Deep compare | 0.37847s | | **Difference** | | **0.03741s** |

The ~37ms delta over 10M iterations corresponds to nanosecond-level differences per call, which are statistically exploitable under controlled conditions.

## Attack Scenario

1. Attacker intercepts…

Affected: CleanStart: airflow-3

CVE-2026-49265 affects multiple packages. This issue is resolved in later releases. See references for individual vulnerability details.

OAuthLib is an implementation of the OAuth request-signing logic for Python 3.6+. From 3.0.0 until 4.0.0, OAuthLib's PKCE checks in oauthlib/oauth2/rfc6749/grant_types/authorization_code.py compare attacker-supplied code_verifier values with stored challenges using ordinary string equality in code_challenge_method_plain and code_challenge_method_s256. Because the comparison can return after a length difference or the first mismatching character, repeated token endpoint measurements can reveal common-prefix timing information that could potentially allow recovery of the code_verifier, unauthorized access-token acquisition, and account takeover. Practical exploitation requires an intercepted, single-use authorization code and enough measurements to overcome real-world network noise; the local timing benchmark does not establish practical remote account takeover, so the weakness remains a defense-in-depth concern. This issue is fixed in version 4.0.0.

Affected: PyPI: oauthlib

## Summary

A timing side-channel vulnerability exists in the PKCE (RFC 7636) implementation of the Authorization Code Grant flow. The `code_challenge_method_plain` function uses Python's standard `==` operator for string comparison instead of a constant-time comparison function, potentially allowing timing-based attacks.

## Affected Component

- File: `oauthlib/oauth2/rfc6749/grant_types/authorization_code.py` - Functions: `code_challenge_method_plain`, `code_challenge_method_s256` - Vulnerability Type: CWE-208 (Observable Timing Discrepancy)

## Technical Details

Python's `==` operator uses short-circuit evaluation when comparing strings: 1. Returns `False` immediately if lengths differ 2. Compares characters left-to-right, stopping at first mismatch

This means comparison time varies linearly with the length of the common prefix between the attacker-supplied verifier and the stored challenge, creating a measurable timing oracle.

## Proof of Concept

Tested locally against oauthlib source (network jitter eliminated to isolate pure Python execution time):

| Input | Result | Time (10M iterations) | |---|---|---| | Wrong first char (`B` + `A`*49) | Fast reject | 0.34106s | | 49 chars correct (`A`*49 + `B`) | Deep compare | 0.37847s | | **Difference** | | **0.03741s** |

The ~37ms delta over 10M iterations corresponds to nanosecond-level differences per call, which are statistically exploitable under controlled conditions.

## Attack Scenario

1. Attacker intercepts…

Affected: PyPI: oauthlib

## Summary

A timing side-channel vulnerability exists in the PKCE (RFC 7636) implementation of the Authorization Code Grant flow. The `code_challenge_method_plain` function uses Python's standard `==` operator for string comparison instead of a constant-time comparison function, potentially allowing timing-based attacks.

## Affected Component

- File: `oauthlib/oauth2/rfc6749/grant_types/authorization_code.py` - Functions: `code_challenge_method_plain`, `code_challenge_method_s256` - Vulnerability Type: CWE-208 (Observable Timing Discrepancy)

## Technical Details

Python's `==` operator uses short-circuit evaluation when comparing strings: 1. Returns `False` immediately if lengths differ 2. Compares characters left-to-right, stopping at first mismatch

This means comparison time varies linearly with the length of the common prefix between the attacker-supplied verifier and the stored challenge, creating a measurable timing oracle.

## Proof of Concept

Tested locally against oauthlib source (network jitter eliminated to isolate pure Python execution time):

| Input | Result | Time (10M iterations) | |---|---|---| | Wrong first char (`B` + `A`*49) | Fast reject | 0.34106s | | 49 chars correct (`A`*49 + `B`) | Deep compare | 0.37847s | | **Difference** | | **0.03741s** |

The ~37ms delta over 10M iterations corresponds to nanosecond-level differences per call, which are statistically exploitable under controlled conditions.

## Attack Scenario

1. Attacker intercepts…

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Security update for python-oauthlib