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CVE-2026-85394

python-jose through 3.5.0 Algorithm Confusion via DER-encoded Public Key as HMAC Secret

9.3 CriticalFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

0.22%Unchanged since Sep 4, 2026
90%50%10%1%

What each source reports

CVE List Score used 9.3

python-jose through 3.5.0 Algorithm Confusion via DER-encoded Public Key as HMAC Secret

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.

Record
CVE-2026-85394
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-347
Updated
2026-11-02
EUVDEUVD-2026-70671 9.3

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.

Record
EUVD-2026-70671
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-3qf3-8w2g-rqmx 9.3

python-jose algorithm confusion guard bypassed by DER-encoded public keys

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.

Record
GHSA-3qf3-8w2g-rqmx
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-347
Updated
2026-11-02
NVD 9.3

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.

Record
CVE-2026-85394
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-347
Updated
2026-11-02
OSVCVE-2024-33663 6.5

python-jose through 3.3.0 has algorithm confusion with OpenSSH ECDSA keys and other key formats. This is similar to CVE-2022-29217.

Record
CVE-2024-33663
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Updated
2026-11-02
OSV 9.3

python-jose through 3.5.0 Algorithm Confusion via DER-encoded Public Key as HMAC Secret

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.

Record
CVE-2026-85394
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Weakness
CWE-347
Updated
2026-11-02
Show 7 moreShow less
OSVGHSA-3qf3-8w2g-rqmx 9.3

python-jose algorithm confusion guard bypassed by DER-encoded public keys

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.

Record
GHSA-3qf3-8w2g-rqmx
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-347
Updated
2026-11-02
OSVGHSA-6c5p-j8vq-pqhj 9.3

python-jose algorithm confusion with OpenSSH ECDSA keys

python-jose through 3.3.0 has algorithm confusion with OpenSSH ECDSA keys and other key formats. This is similar to CVE-2022-29217.

Record
GHSA-6c5p-j8vq-pqhj
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-327
Updated
2026-11-02
OSVPYSEC-2026-4298 9.3

python-jose algorithm confusion guard bypassed by DER-encoded public keys

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.

Record
PYSEC-2026-4298
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Updated
2026-11-02
OSVUBUNTU-CVE-2026-85394 9.3

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.

Record
UBUNTU-CVE-2026-85394
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Updated
2026-11-02
OSVCLSA-2026-1791441237 No score

TuxCare security update for python-jose (1 CVE)

TuxCare rebuilt python-jose to address 1 CVE. Fixed in 3.3.0.post3+tuxcare.

Record
CLSA-2026-1791441237
Updated
2026-11-02
OSVPYSEC-2024-232 No score

python-jose through 3.3.0 has algorithm confusion with OpenSSH ECDSA keys and other key formats. This is similar to CVE-2022-29217.

Record
PYSEC-2024-232
Updated
2026-11-02
OSVROOT-APP-PYPI-CVE-2026-85394 No score

CVE-2026-85394 in python-jose - Patched by Root

Root has patched CVE-2026-85394 in the python-jose package for Root:PyPI. Multiple fixed versions available.

Record
ROOT-APP-PYPI-CVE-2026-85394
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
python-jose
PyPI
 through 3.5.0 None known
python-jose
TuxCare:PyPI
 3.3.0 up to 3.3.0.post3+tuxcare, plus listed versions
3.3.0.post1+tuxcare3.3.0.post2+tuxcare
3.3.0.post3+tuxcare
python-jose
PyPI
From an advisory covering 2 CVEs
 through 3.5.0, plus listed versions
0.1.00.1.10.1.20.1.30.1.4
Show 33 moreShow less
0.1.50.1.60.1.70.1.80.2.00.3.00.4.00.5.00.5.10.5.20.5.30.5.40.5.50.5.60.6.10.6.20.7.01.0.01.1.01.2.01.3.01.3.11.3.21.4.02.0.02.0.12.0.23.0.03.0.13.1.03.2.03.3.03.4.0
 None known
python-jose
PyPI
From an advisory covering 2 CVEs
 before 3.4.0, plus listed versions
0.1.00.1.10.1.20.1.30.1.4
Show 32 moreShow less
0.1.50.1.60.1.70.1.80.2.00.3.00.4.00.5.00.5.10.5.20.5.30.5.40.5.50.5.60.6.10.6.20.7.01.0.01.1.01.2.01.3.01.3.11.3.21.4.02.0.02.0.12.0.23.0.03.0.13.1.03.2.03.3.0
3.4.0
python-jose
Root:PyPI
 before 3.5.0+aikido.1
3.5.0+aikido.1
python-jose
Ubuntu:22.04:LTS
 All versions, plus listed versions
3.3.0+dfsg-1
 None known
python-jose
Ubuntu:24.04:LTS
 All versions, plus listed versions
3.3.0+dfsg-4
 None known

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-85394 is a critical vulnerability (CVSS 9.3) in Mpdavis Python-jose, published April 25, 2024. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.22%, the 12th percentile. Fixed in python-jose 3.3.0.post3+tuxcare.

References

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