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CVE-2026-33996

LibJWT has NULL/bounds validation in JWK octet and RSA PSS parsing

5.8 MediumFix available

LibJWT is a C JSON Web Token Library. Starting in version 3.0.0 and prior to version 3.3.0, the JWK parsing for RSA-PSS did not protect against a NULL value when expecting to parse JSON string values. A specially crafted JWK file could exploit this behavior by using integers in places where the code expected a string. This was fixed in v3.3.0. A workaround is available. Users importing keys through a JWK file should not do so from untrusted sources. Use the jwk2key tool to check for validity of a JWK file. Likewise, if possible, do not use JWK files with RSA-PSS keys.

Attack profile

How easy it is to exploit

Attack vector
Adjacent network
Complexity
High
Privileges needed
None
User interaction
Active

What an attacker can affect

Confidentiality
Low
Integrity
Low
Availability
High

Exploit likelihood

0.16%Up 0.1 points since Mar 28, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.8

LibJWT has NULL/bounds validation in JWK octet and RSA PSS parsing

LibJWT is a C JSON Web Token Library. Starting in version 3.0.0 and prior to version 3.3.0, the JWK parsing for RSA-PSS did not protect against a NULL value when expecting to parse JSON string values. A specially crafted JWK file could exploit this behavior by using integers in places where the code expected a string. This was fixed in v3.3.0. A workaround is available. Users importing keys through a JWK file should not do so from untrusted sources. Use the jwk2key tool to check for validity of a JWK file. Likewise, if possible, do not use JWK files with RSA-PSS keys.

Record
CVE-2026-33996
CVSS 4.0
5.8 MediumCVSS:4.0/AV:A/AC:H/AT:P/PR:N/UI:A/VC:L/VI:L/VA:H/SC:L/SI:L/SA:L
Weakness
CWE-476
Updated
2026-11-02
EUVDEUVD-2026-16899 5.8

LibJWT is a C JSON Web Token Library. Starting in version 3.0.0 and prior to version 3.3.0, the JWK parsing for RSA-PSS did not protect against a NULL value when expecting to parse JSON string values. A specially crafted JWK file could exploit this behavior by using integers in places where the code expected a string. This was fixed in v3.3.0. A workaround is available. Users importing keys through a JWK file should not do so from untrusted sources. Use the jwk2key tool to check for validity of a JWK file. Likewise, if possible, do not use JWK files with RSA-PSS keys.

Record
EUVD-2026-16899
CVSS 4.0
5.8 MediumCVSS:4.0/AV:A/AC:H/AT:P/PR:N/UI:A/VC:L/VI:L/VA:H/SC:L/SI:L/SA:L
Updated
2026-11-02
NVD 5.8

LibJWT is a C JSON Web Token Library. Starting in version 3.0.0 and prior to version 3.3.0, the JWK parsing for RSA-PSS did not protect against a NULL value when expecting to parse JSON string values. A specially crafted JWK file could exploit this behavior by using integers in places where the code expected a string. This was fixed in v3.3.0. A workaround is available. Users importing keys through a JWK file should not do so from untrusted sources. Use the jwk2key tool to check for validity of a JWK file. Likewise, if possible, do not use JWK files with RSA-PSS keys.

Record
CVE-2026-33996
CVSS 4.0
5.8 MediumCVSS:4.0/AV:A/AC:H/AT:P/PR:N/UI:A/VC:L/VI:L/VA:H/SC:L/SI:L/SA:L/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
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Weakness
CWE-476
Updated
2026-11-02
OSV 5.8

LibJWT has NULL/bounds validation in JWK octet and RSA PSS parsing

LibJWT is a C JSON Web Token Library. Starting in version 3.0.0 and prior to version 3.3.0, the JWK parsing for RSA-PSS did not protect against a NULL value when expecting to parse JSON string values. A specially crafted JWK file could exploit this behavior by using integers in places where the code expected a string. This was fixed in v3.3.0. A workaround is available. Users importing keys through a JWK file should not do so from untrusted sources. Use the jwk2key tool to check for validity of a JWK file. Likewise, if possible, do not use JWK files with RSA-PSS keys.

Record
CVE-2026-33996
CVSS 4.0
5.8 MediumCVSS:4.0/AV:A/AC:H/AT:P/PR:N/UI:A/VC:L/VI:L/VA:H/SC:L/SI:L/SA:L
Weakness
CWE-476
Updated
2026-11-02
OSVDEBIAN-CVE-2026-33996 5.5

LibJWT is a C JSON Web Token Library. Starting in version 3.0.0 and prior to version 3.3.0, the JWK parsing for RSA-PSS did not protect against a NULL value when expecting to parse JSON string values. A specially crafted JWK file could exploit this behavior by using integers in places where the code expected a string. This was fixed in v3.3.0. A workaround is available. Users importing keys through a JWK file should not do so from untrusted sources. Use the jwk2key tool to check for validity of a JWK file. Likewise, if possible, do not use JWK files with RSA-PSS keys.

Record
DEBIAN-CVE-2026-33996
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2026-33996 5.8

LibJWT is a C JSON Web Token Library. Starting in version 3.0.0 and prior to version 3.3.0, the JWK parsing for RSA-PSS did not protect against a NULL value when expecting to parse JSON string values. A specially crafted JWK file could exploit this behavior by using integers in places where the code expected a string. This was fixed in v3.3.0. A workaround is available. Users importing keys through a JWK file should not do so from untrusted sources. Use the jwk2key tool to check for validity of a JWK file. Likewise, if possible, do not use JWK files with RSA-PSS keys.

Record
UBUNTU-CVE-2026-33996
CVSS 4.0
5.8 MediumCVSS:4.0/AV:A/AC:H/AT:P/PR:N/UI:A/VC:L/VI:L/VA:H/SC:L/SI:L/SA:L
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
libjwt3
Debian:14
before 3.3.2-1, plus listed versions
3.2.2-13.2.3-1
3.3.2-1
libjwt
Ubuntu:18.04:LTS
All versions, plus listed versions
1.8.0+dfsg-11.8.0+dfsg-21.9.0-11.9.0-1build1
None known
libjwt
Ubuntu:20.04:LTS
All versions, plus listed versions
1.10.2-1
None known
libjwt
Ubuntu:22.04:LTS
All versions, plus listed versions
1.10.2-11.10.2-1build1
None known
libjwt
Ubuntu:24.04:LTS
All versions, plus listed versions
1.10.2-1build11.17.0-21.17.0-2build11.17.0-2build2
None known
libjwt
Ubuntu:25.10
All versions, plus listed versions
1.17.2-1
None known
libjwt
Ubuntu:26.10
All versions, plus listed versions
1.17.2-1build11.17.2-1build2
None known
libjwt3
Ubuntu:26.10
All versions, plus listed versions
3.2.3-13.3.3-13.3.3-1build1
None known
libjwt
Ubuntu:26.04:LTS
All versions, plus listed versions
1.17.2-11.17.2-1build1
None known
libjwt3
Ubuntu:26.04:LTS
All versions, plus listed versions
3.2.2-13.2.3-1
None known

History

History
RecordedChangedSources
first indexedCVE List, EUVD, NVD, OSV

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

In short

CVE-2026-33996 is a medium vulnerability (CVSS 5.8) in Benmcollins Libjwt, published March 27, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.16%, the 4th percentile. Fixed in libjwt3 3.3.2-1.

References

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