CVE-2026-34986: Go JOSE affect by a panic in JWE decryption
Impact
Decrypting a JSON Web Encryption (JWE) object will panic if the alg field indicates a key wrapping algorithm (one ending in KW, with the exception of A128GCMKW, A192GCMKW, and A256GCMKW) and the encryptedkey field is empty. The panic happens when cipher.KeyUnwrap() in keywrap.go attempts to allocate a slice with a zero or negative length based on the length of the encryptedkey.
This code path is reachable from ParseEncrypted() / ParseEncryptedJSON() / ParseEncryptedCompact() followed by Decrypt() on the resulting object. Note that the parse functions take a list of accepted key algorithms. If the accepted key algorithms do not include any key wrapping algorithms, parsing will fail and the application will be unaffected.
This panic is also reachable by calling cipher.KeyUnwrap() directly with any ciphertext parameter less than 16 bytes long, but calling this function directly is less common.
Panics can lead to denial of service.
Fixed In
4.1.4 and v3.0.5
Workarounds
If the list of keyAlgorithms passed to ParseEncrypted() / ParseEncryptedJSON() / ParseEncryptedCompact() does not include key wrapping algorithms (those ending in KW), your application is unaffected.
If your application uses key wrapping, you can prevalidate to the JWE objects to ensure the encryptedkey field is nonempty. If your application accepts JWE Compact Serialization, apply that validation to the corresponding field of that serialization (the data between the first and second .).
Thanks
Go JOSE thanks Datadog's Security team for finding this issue.
Other sources
Go JOSE provides an implementation of the Javascript Object Signing and Encryption set of standards in Go, including support for JSON Web Encryption (JWE), JSON Web Signature (JWS), and JSON Web Token (JWT) standards. Prior to 4.1.4 and 3.0.5, decrypting a JSON Web Encryption (JWE) object will panic if the alg field indicates a key wrapping algorithm (one ending in KW, with the exception of A128GCMKW, A192GCMKW, and A256GCMKW) and the encryptedkey field is empty. The panic happens when cipher.KeyUnwrap() in keywrap.go attempts to allocate a slice with a zero or negative length based on the length of the encryptedkey. This code path is reachable from ParseEncrypted() / ParseEncryptedJSON() / ParseEncryptedCompact() followed by Decrypt() on the resulting object. Note that the parse functions take a list of accepted key algorithms. If the accepted key algorithms do not include any key wrapping algorithms, parsing will fail and the application will be unaffected. This panic is also reachable by calling cipher.KeyUnwrap() directly with any ciphertext parameter less than 16 bytes long, but calling this function directly is less common. Panics can lead to denial of service. This vulnerability is fixed in 4.1.4 and 3.0.5.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/github.com/go-jose/go-jose/v3to a version that resolves this vulnerability.Fixed in 3.0.5 - Upgrade
Upgrade
go/github.com/go-jose/go-jose/v4to a version that resolves this vulnerability.Fixed in 4.1.4 - Upgrade
Upgrade
go-joseto a version that resolves this vulnerability.Fixed in 4.1.4 - Upgrade
Upgrade
go-joseto a version that resolves this vulnerability.Fixed in 3.0.5 - Configuration
Ensure the accepted key algorithms passed to ParseEncrypted(), ParseEncryptedJSON(), or ParseEncryptedCompact() do not include key wrapping algorithms (alg values ending in KW). If your list of keyAlgorithms does not include key wrapping algorithms, the application is unaffected.
Go JOSE JWE parsing/decryption keyAlgorithms list for ParseEncrypted()/ParseEncryptedJSON()/ParseEncryptedCompact() = exclude key wrapping algorithms (alg values ending in KW, except A128GCMKW, A192GCMKW, A256GCMKW) - Configuration
If your application accepts JWE Compact Serialization, apply validation to the corresponding field in that serialization (the data between the first and second '.') to ensure the encrypted_key is nonempty before attempting decryption.
JWE Compact Serialization validation encrypted_key field validation for Compact Serialization = reject/validate when encrypted_key is empty - Compensating control
Prevalidate JWE objects so that when the JWE header 'alg' indicates a key wrapping algorithm (ending in 'KW', with the exception of A128GCMKW, A192GCMKW, and A256GCMKW), the JWE 'encrypted_key' field is nonempty; this prevents the reachable panic path during ParseEncrypted*/Decrypt().