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CVE-2026-116585: Go JOSE: Panic during CBC-HMAC processing

• Severity: medium (CVSS 6.9 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-26 · updated 2026-10-31
• Weakness: CWE-129

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.

Affected products

• go-jose: before 4.1.5

References

• https://github.com/go-jose/go-jose/commit/35883f7999e87cbd1b1f4cda07fdad8cd71c3dd6
• https://github.com/go-jose/go-jose/commit/74114c2fa22669a2b2a296746eaa82e15566fd54
• https://github.com/go-jose/go-jose/pull/292
• https://github.com/go-jose/go-jose/releases/tag/v4.1.5
• https://github.com/go-jose/go-jose/security/advisories/GHSA-4w3g-jfj2-cw2q

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