CVE-2024-5535: OpenSSL · Out-of-bounds Read
Affects OpenSSLSource GCVE Database
Not known to be exploited · CVSS 9.1 Critical.
Data as of 6 Nov 2026, 23:23 UTC
Thin evidence
One scorer or none| CISA-ADP | CVSS 3.1 | 9.1 |
|---|
- 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:HExploitation evidence
Disclosed: evidence found.
CVE published 27 Jun 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
Public exploit code: GitHub proofs of concept
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
GitHubopenssl/opensslpkg:github/openssl/opensslOther threats | Affected
| 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
- openssl.org/news/secadv/20240627.txt (opens in a new tab)
- github.com/openssl/openssl/commit/e86ac436f0bd54d4517745483e2315650fae7b2c (opens in a new tab)
- github.com/openssl/openssl/commit/99fb785a5f85315b95288921a321a935ea29a51e (opens in a new tab)
- github.com/openssl/openssl/commit/4ada436a1946cbb24db5ab4ca082b69c1bc10f37 (opens in a new tab)
- github.com/openssl/openssl/commit/cf6f91f6121f4db167405db2f0de410a456f260c (opens in a new tab)
- github.openssl.org/openssl/extended-releases/commit/b78ec0824da857223486660177d3b1f255c65d87 (opens in a new tab)
- github.openssl.org/openssl/extended-releases/commit/9947251413065a05189a63c9b7a6c1d4e224c21c (opens in a new tab)
- openwall.com/lists/oss-security/2024/06/27/1 (opens in a new tab)
- openwall.com/lists/oss-security/2024/06/28/4 (opens in a new tab)
- security.netapp.com/advisory/ntap-20240712-0005/ (opens in a new tab)
- openwall.com/lists/oss-security/2024/08/15/1 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2024/11/msg00000.html (opens in a new tab)
- lists.debian.org/debian-lts-announce/2024/10/msg00033.html (opens in a new tab)
- security.netapp.com/advisory/ntap-20241025-0010/ (opens in a new tab)
- security.netapp.com/advisory/ntap-20241025-0006/ (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-398330.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-265688.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-915275.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-769027.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-277137.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-613116.html (opens in a new tab)