Go JOSE: Panic during CBC-HMAC processing

MEDIUM 6.9CVE-2026-116585 · GHSA-4w3g-jfj2-cw2q · Published 26/10/2026 · updated 31/10/2026

In short

CVE-2026-116585 is a MEDIUM (CVSS 6.9) vulnerability affecting github.com/go-jose/go-jose/v3, github.com/go-jose/go-jose/v4.
Chance of exploitation in the next 30 days (EPSS): 0.26%, higher than 18.4% of all vulnerabilities.
Fix: update to 4.1.5 or later.

Package	Affected versions	Patched versions
github.com/go-jose/go-jose/v3 Go	`≤ 3.0.5`	No fix yet
github.com/go-jose/go-jose/v4 Go	`< 4.1.5`	`4.1.5`

Description

Summary

Decrypting a ciphertext with "A128CBC-HS256", "A192CBC-HS384", or "A256CBC-HS512" can result in a panic on untrusted input.

Note this advisory is the same as https://github.com/go-jose/go-jose/security/advisories/GHSA-6mp9-8xrw-74r4.

Details

Insufficient validation of parameters can lead to attempting to index into an empty buffer. See https://github.com/go-jose/go-jose/pull/292.

Workarounds

If the application does not require the CBC-HMAC modes for content encryption, and is using github.com/go-jose/go-jose/v4, do not include them in the list of ContentEncryption algorithms passed to ParseEncrypted / ParseEncryptedJSON / ParseEncryptedCompact.

Impact

Denial of service vulnerability. Any application which decrypts untrusted ciphertexts with the indicated algorithms is affected.

Acknowledgements

Thanks to Joshua Rogers of AISLE Research for reporting this problem.

NVD description

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 4.1.5, decrypting untrusted JWE ciphertext with A128CBC-HS256, A192CBC-HS384, or A256CBC-HS512 can pass an empty ciphertext buffer to CBC-HMAC unpadding. Insufficient validation allows the empty buffer to be indexed, causing a panic and denial of service. Applications that decrypt attacker-controlled ciphertext with one of these content-encryption algorithms are affected. This issue is fixed in version 4.1.5.