CVE-2021-29444
Padding Oracle Attack due to Observable Timing Discrepancy in jose-browser-runtime
jose-browser-runtime is an npm package which provides a number of cryptographic functions. In versions prior to 3.11.4 the AES_CBC_HMAC_SHA2 Algorithm (A128CBC-HS256, A192CBC-HS384, A256CBC-HS512) decryption would always execute both HMAC tag verification and CBC decryption, if either failed JWEDecryptionFailed would be thrown. But a possibly observable difference in timing when padding error would occur while decrypting the ciphertext makes a padding oracle and an adversary might be able to make use of that oracle to decrypt data without knowing the decryption key by issuing on average 128*b calls to the padding oracle (where b is the number of bytes in the ciphertext block). A patch was released which ensures the HMAC tag is verified before performing CBC decryption. The fixed versions are >=3.11.4. Users should upgrade to ^3.11.4.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Padding Oracle Attack due to Observable Timing Discrepancy in jose-browser-runtime
jose-browser-runtime is an npm package which provides a number of cryptographic functions. In versions prior to 3.11.4 the AES_CBC_HMAC_SHA2 Algorithm (A128CBC-HS256, A192CBC-HS384, A256CBC-HS512) decryption would always execute both HMAC tag verification and CBC decryption, if either failed JWEDecryptionFailed would be thrown. But a possibly observable difference in timing when padding error would occur while decrypting the ciphertext makes a padding oracle and an adversary might be able to make use of that oracle to decrypt data without knowing the decryption key by issuing on average 128*b calls to the padding oracle (where b is the number of bytes in the ciphertext block). A patch was released which ensures the HMAC tag is verified before performing CBC decryption. The fixed versions are >=3.11.4. Users should upgrade to ^3.11.4.
- Record
CVE-2021-29444- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-203
- Updated
- 2026-11-02
EUVDEUVD-2021-0803
jose-browser-runtime is an npm package which provides a number of cryptographic functions. In versions prior to 3.11.4 the AES_CBC_HMAC_SHA2 Algorithm (A128CBC-HS256, A192CBC-HS384, A256CBC-HS512) decryption would always execute both HMAC tag verification and CBC decryption, if either failed JWEDecryptionFailed would be thrown. But a possibly observable difference in timing when padding error would occur while decrypting the ciphertext makes a padding oracle and an adversary might be able to make use of that oracle to decrypt data without knowing the decryption key by issuing on average 128*b calls to the padding oracle (where b is the number of bytes in the ciphertext block). A patch was released which ensures the HMAC tag is verified before performing CBC decryption. The fixed versions are >=3.11.4. Users should upgrade to ^3.11.4.
- Record
EUVD-2021-0803- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-94hh-pjjg-rwmr
Padding Oracle Attack due to Observable Timing Discrepancy in jose-browser-runtime
Impact
AES_CBC_HMAC_SHA2 Algorithm (A128CBC-HS256, A192CBC-HS384, A256CBC-HS512) decryption would always execute both HMAC tag verification and CBC decryption, if either failed JWEDecryptionFailed would be thrown. But a possibly observable difference in timing when padding error would occur while decrypting the ciphertext makes a padding oracle and an adversary might be able to make use of that oracle to decrypt data without knowing the decryption key by issuing on average 128*b calls to the padding oracle (where b is the number of bytes in the ciphertext block).
Patches
A patch was released which ensures the HMAC tag is verified before performing CBC decryption. The fixed versions are >=3.11.4.
Users should upgrade to ^3.11.4.
Credits
Thanks to Morgan Brown of Microsoft for bringing this up and Eva Sarafianou (@esarafianou) for helping to score this advisory.
- Record
GHSA-94hh-pjjg-rwmr- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-203
- Updated
- 2026-11-02
NVD
jose-browser-runtime is an npm package which provides a number of cryptographic functions. In versions prior to 3.11.4 the AES_CBC_HMAC_SHA2 Algorithm (A128CBC-HS256, A192CBC-HS384, A256CBC-HS512) decryption would always execute both HMAC tag verification and CBC decryption, if either failed JWEDecryptionFailed would be thrown. But a possibly observable difference in timing when padding error would occur while decrypting the ciphertext makes a padding oracle and an adversary might be able to make use of that oracle to decrypt data without knowing the decryption key by issuing on average 128*b calls to the padding oracle (where b is the number of bytes in the ciphertext block). A patch was released which ensures the HMAC tag is verified before performing CBC decryption. The fixed versions are >=3.11.4. Users should upgrade to ^3.11.4.
- Record
CVE-2021-29444- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:P/I:N/A:N - Weakness
- CWE-203
- Updated
- 2026-11-02
OSV
jose-browser-runtime is an npm package which provides a number of cryptographic functions. In versions prior to 3.11.4 the AES_CBC_HMAC_SHA2 Algorithm (A128CBC-HS256, A192CBC-HS384, A256CBC-HS512) decryption would always execute both HMAC tag verification and CBC decryption, if either failed JWEDecryptionFailed would be thrown. But a possibly observable difference in timing when padding error would occur while decrypting the ciphertext makes a padding oracle and an adversary might be able to make use of that oracle to decrypt data without knowing the decryption key by issuing on average 128*b calls to the padding oracle (where b is the number of bytes in the ciphertext block). A patch was released which ensures the HMAC tag is verified before performing CBC decryption. The fixed versions are >=3.11.4. Users should upgrade to ^3.11.4.
- Record
CVE-2021-29444- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
OSVGHSA-94hh-pjjg-rwmr
Padding Oracle Attack due to Observable Timing Discrepancy in jose-browser-runtime
Impact
AES_CBC_HMAC_SHA2 Algorithm (A128CBC-HS256, A192CBC-HS384, A256CBC-HS512) decryption would always execute both HMAC tag verification and CBC decryption, if either failed JWEDecryptionFailed would be thrown. But a possibly observable difference in timing when padding error would occur while decrypting the ciphertext makes a padding oracle and an adversary might be able to make use of that oracle to decrypt data without knowing the decryption key by issuing on average 128*b calls to the padding oracle (where b is the number of bytes in the ciphertext block).
Patches
A patch was released which ensures the HMAC tag is verified before performing CBC decryption. The fixed versions are >=3.11.4.
Users should upgrade to ^3.11.4.
Credits
Thanks to Morgan Brown of Microsoft for bringing this up and Eva Sarafianou (@esarafianou) for helping to score this advisory.
- Record
GHSA-94hh-pjjg-rwmr- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-203
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
jose-browser-runtimenpm |
before 3.11.4 | 3.11.4 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, products | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-29444 is a medium vulnerability (CVSS 5.9) in Appsup-dart Jose, published April 16, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.07%, the 64th percentile. Fixed in jose-browser-runtime 3.11.4.