OpenSSL Vulnerability: NULL Pointer Dereference in QUIC Protocol Handling

openssl Updated 28 Jan 2026

Summary

27/01/2026

Disclosed on

N/A

Severity

Yes i

Fix available

Unrated

Severity

Not published

CVSS Score

ALPINE-CVE-2025-15468: Issue summary: If an application using the SSL_CIPHER_find() function in a QUIC protocol client or server receives an unknown cipher suite from the peer, a NULL dereference occurs. Affects openssl versions < 3.3.6-r0. Fixed in 3.3.6-r0. How to fix ↓

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Background

OpenSSL is a widely-used open-source library that provides robust cryptographic functions and protocols, including SSL and TLS for secure communication over networks. The library supports various protocols, including QUIC, which is designed for low-latency communication. However, the introduction of QUIC support in version 3.2 has led to a vulnerability where an unknown cipher suite can cause a NULL pointer dereference, resulting in a Denial of Service (DoS) condition.

Vulnerability Detail

The vulnerability arises from the SSL_CIPHER_find() function being called in the client_hello_cb callback when an application receives an unknown cipher suite from a peer. If the cipher ID is unsupported, it leads to a NULL pointer dereference, causing the application to terminate unexpectedly. This issue was introduced with the QUIC protocol support in OpenSSL version 3.2 and affects versions 3.3 to 3.6. While the impact is assessed as low severity due to the limited use of this function in QUIC applications, it still poses a risk of service disruption.

How To Fix

Minimum fixed version

3.3.6-r0

This is the first release that contains the fix.

sudo apk add --upgrade openssl

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Workaround

As a workaround, applications can implement additional checks before calling the SSL_CIPHER_find() function to ensure that the cipher ID received is valid and supported. This can prevent the NULL pointer dereference from occurring.

Conclusion

In summary, the OpenSSL vulnerability related to NULL pointer dereference in QUIC protocol handling poses a risk of Denial of Service. Users are advised to update their OpenSSL packages to the latest patched versions to mitigate this issue. Additionally, implementing workarounds can help reduce the risk until updates are applied.

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