VulnSocial

CVE-2026-85394Disclosure

LOWCVSS 9.3 · CRITICAL

Signal is active with 1 mentions in latest observed window

Immediate actions

  • Patch affected systems immediately

Recommended action window: Monitor and triage in normal cycle

NVD description

python-jose through 3.5.0 fails to properly validate asymmetric keys in HMAC initialization, accepting DER-encoded public keys that lack PEM armor or SSH prefixes. Attackers holding the service's public key can forge HS256 tokens that pass verification when algorithms are not explicitly restricted. This is an incomplete fix for CVE-2024-33663.

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0.5/ 10 priority

Sources & remediation

Other references
Weakness type (CWE)
CWE-347

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

AVAILABLE

Momentum

STABLE

Threat summary

  • Patch or workaround signal is available
  • 5 mentions across 3 observed days
  • Momentum state: stable

What's happening

  • Patch or workaround mentioned in 1 signal
  • Technical details provided in 5 signals
  • Disclosure: 5 classified signals
  • Peaked 1d ago at 3 mentions (2026-09-04); latest day: 1
  • 5 total mentions across 3 days

Deep dive

Activity timeline5 mentions / 3d
01223Mentions · 2026-09-03: 1Mentions · 2026-09-04: 3Mentions · 2026-09-05: 1Patch / Workaround · 2026-09-05: 1Technical Details · 2026-09-03: 1Technical Details · 2026-09-04: 3Technical Details · 2026-09-05: 109-0309-0409-05
Signal classification1 categories
Disclosure
5100.0%
Referenced assets3 URLs
Classification over time
DateTotalLabels
2026-09-031
Disclosure1
2026-09-043
Disclosure3
2026-09-051
Disclosure1
Full discourse5 posts
  • Cyber Threat Observatory | Alan Turing Institute@TuringCyberObs
    Disclosure

    CVE-2026-85394 python-jose JWT algorithm confusion could let attackers forge tokens where applications rely on default algorithm handling with DER-encoded public keys Full analysis: https://github.com/alan-turing-institute/cyber-threat-observatory/blob/main/reports/2026-09-03/TIER_2_CVE-2026-85394.md #CyberSecurity #IdentitySecurity #VulnerabilityManagement

    Post summary

    The post announces CVE‑2026‑85394, a JWT algorithm‑confusion flaw in python‑jose that could enable attackers to forge tokens using DER‑encoded public keys, and links to a detailed analysis report.

    0101024
    61 followersView on X
  • Upwind Security MDR@UpwindMDR
    Disclosure

    🚨 Critical - python-jose JWT Algorithm Confusion via DER Key Acceptance (CVE-2026-85394) python-jose <=3.5.0 mishandles asymmetric keys during HMAC initialization, accepting DER-encoded public keys without PEM armor or an SSH prefix. If JWT verification does not strictly restrict algorithms, an attacker with the service’s public key can forge HS256 tokens that validate and bypass authentication. This is an incomplete fix for CVE-2024-33663. 👉 Affected: python-jose <= 3.5.0

    Post summary

    The text discloses CVE-2026-85394, explaining how DER‑encoded public keys can be used to forge HS256 JWTs in python‑jose, but it does not mention any PoC, exploit tool, active exploitation, or available patch.

    0001083
    301 followersView on X
  • 0xAppSec@0xAppSec
    Disclosure

    python-jose through 3.5.0 accepts a DER-encoded public key as an HMAC secret. Anyone with your public key can forge HS256 tokens that verify. CVE-2026-85394, an incomplete fix for the same class from 2024. Pin the algorithm at verification. Never let the token choose it.

    Post summary

    Python‑jose v3.5.0 incorrectly treats DER‑encoded public keys as HMAC secrets, allowing HS256 token forgery. CVE‑2026‑85394 is an incomplete fix; recommended mitigation is to pin the algorithm at verification.

    0000041
    34 followersView on X
  • Severity Daily@severitydaily
    Disclosure

    python-jose still lets a public key serve as an HMAC secret, because the 2024 fix checked the key format instead of the key. No patched release, no reported exploitation. https://severitydaily.com/python-jose-cve-2026-85394-der-public-key-hmac-incomplete-fix/

    Post summary

    The text notes that python-jose still allows a public key to be used as an HMAC secret because of an incomplete 2024 fix, with no patch released or exploitation reported.

    0000017
    23 followersView on X
  • CVE@CVEnew
    Disclosure

    CVE-2026-85394 python-jose through 3.5.0 fails to properly validate asymmetric keys in HMAC initialization, accepting DER-encoded public keys that lack PEM armor or SSH prefixes. At… https://www.cve.org/CVERecord?id=CVE-2026-85394

    Post summary

    The post briefly describes CVE‑2026‑85394 as a validation flaw in python‑jose, where DER‑encoded keys without PEM armor or SSH prefixes are incorrectly accepted during HMAC initialization.

    000001.1K
    58.1K followersView on X

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