CVE-2026-117656: Acceptance of Extraneous Untrusted Data With Trusted Data vulnerability in the Sign in with Apple strategy in

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CRITICAL 9.3REMOTE

CVE-2026-117656 is a critical-severity flaw (CVSS 9.3) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Acceptance of Extraneous Untrusted Data With Trusted Data vulnerability in the Sign in with Apple strategy in pow-auth Assent allows an unauthenticated remote attacker to impersonate another user via the user parameter of the authorization callback. Apple posts the user's name to the callback endpoint in a user form parameter that the browser submits and the client controls. Assent.Strategy.Apple.callback/2 in lib/assent/strategies/apple.ex deco

Why this priority

Critical severity
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.3 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	n/a
CISA exploited list	No
Weakness	CWE-290, CWE-349
Published	2026-10-31
Last modified	2026-10-31

Publisher (CNA): EEF

Last updated 2026-10-31 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Timeline

2026-10-31 00:16 UTCPublished CVE record published
2026-10-31 00:16 UTCUpdated Record last modified

Advisories and coverage

Research and news

VulDB Recent Entries: CVE-2026-117656 | pow-auth assent up to 0.3.1 Sign in with Apple Strategy apple.ex Assent.Strategy.Apple.callback user improper authorizatio 2026-10-31
Vulners Bulletins: CVE-2026-117656 Unverified Sign in with Apple callback parameter can override verified ID token claims 2026-10-30
Vulners Bulletins: CVE-2026-117656 Unverified Sign in with Apple callback parameter can override verified ID token claims 2026-10-30
Vulners Bulletins: EEF-CVE-2026-117656 Unverified Sign in with Apple callback parameter can override verified ID token claims 2026-10-30

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-117656?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Is CVE-2026-117656 being exploited?

CVE-2026-117656 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-117656 affect?

CVE-2026-117656 affects affected software. Severity is critical (CVSS 9.3). Acceptance of Extraneous Untrusted Data With Trusted Data vulnerability in the Sign in with Apple strategy in pow-auth Assent allows an unauthenticated remote attacker to impersonate another user via the user parameter of the authorization

How urgent is CVE-2026-117656?

Priority 38/100. Critical severity; Remotely exploitable, no login, no user action

References

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