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VulnerabilityPublished Updated

CVE-2024-5535: OpenSSL · Out-of-bounds Read

Affects OpenSSLSource GCVE Database

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Not known to be exploited · CVSS 9.1 Critical.

Data as of 6 Nov 2026, 23:23 UTC

CVSS 3.1 base score
9.1Critical
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CISA-ADPCVSS 3.19.1
EPSS
5.5% chance of exploitation in 30 days – higher than 92% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 27 Jun 2024

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    Public exploit code: GitHub proofs of concept

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), GitHub proofs of concept, the Metasploit, Exploit-DB and nuclei-templates index as of 7 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
GitHubopenssl/opensslpkg:github/openssl/opensslOther threatsAffected
  • 1.0.2 – 3.3.0
6 affected builds
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

No immediate action is required as OpenSSL has not released patches for this issue due to its low severity and limited exploitability. The vendor plans to include a fix in future releases. Applications should ensure they do not call SSL_select_next_proto with an empty client protocol list and properly handle no-overlap cases in protocol negotiation. Using ALPN instead of NPN is recommended, as ALPN implementations are not vulnerable to this issue.

Description

CVE-2024-5535 is an out-of-bounds read vulnerability in the OpenSSL function SSL_select_next_proto. This occurs when the function is called with an empty client protocols buffer, potentially causing a crash or leaking up to 255 bytes of arbitrary private memory data to the peer. The issue mainly affects applications that incorrectly call this function with a zero-length client protocol list, which is typically a configuration or programming error. The vulnerability is considered low severity by OpenSSL due to limited exploitability and the requirement of application misconfiguration. No patches have been released yet, but a fix is planned for future OpenSSL releases.

References

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