CVE-2024-2511 Unbounded memory growth with session handling in TLSv1.3

What is CVE-2024-2511?

CVE-2024-2511 is a medium-severity denial of service vulnerability in OpenSSL, published on 8 Apr 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Issue summary: Some non-default TLS server configurations can cause unbounded memory growth when processing TLSv1.3 sessions

Impact summary: An attacker may exploit certain server configurations to trigger unbounded memory growth that would lead to a Denial of Service

This problem can occur in TLSv1.3 if the non-default SSL_OP_NO_TICKET option is being used (but not if early_data support is also configured and the default anti-replay protection is in use). In this case, under certain conditions, the session cache can get into an incorrect state and it will fail to flush properly as it fills. The session cache will continue to grow in an unbounded manner. A malicious client could deliberately create the scenario for this failure to force a Denial of Service. It may also happen by accident in normal operation.

This issue only affects TLS servers supporting TLSv1.3. It does not affect TLS clients.

The FIPS modules in 3.2, 3.1 and 3.0 are not affected by this issue. OpenSSL 1.0.2 is also not affected by this issue.

Weakness: CWE-1325

Which versions are affected by CVE-2024-2511?

How do I fix CVE-2024-2511?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2024-2511 being exploited?

There is no known exploitation of CVE-2024-2511 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2024-2511, AZL-39794, AZL-39797, AZL-40192, AZL-42700, AZL-42765 and 20 more.