OpenSSL: Use After Free
CVE-2026-28387 is a high-severity use after free vulnerability in OpenSSL, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 3.6.2, 3.5.6, 3.4.5 as the first without the flaw, so updating OpenSSL to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.7% chance of exploitation within 30 days, higher than 54% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update OpenSSL to 3.6.2 or 3.5.6 or 3.4.5 or 3.3.7, whichever matches your release line, or a later version.
- Update SIMATIC CN 4100 to V5.0 or a later version.
- Read the advisory on openssl-library.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| OpenSSL | OpenSSL | 3.6.0 up to, but not including, 3.6.2; 3.5.0 up to, but not including, 3.5.6; 3.4.0 up to, but not including, 3.4.5; 3.3.0 up to, but not including, 3.3.7; 3.0.0 up to, but not including, 3.0.20; 1.1.1 up to, but not including, 1.1.1zg | 3.6.2, 3.5.6, 3.4.5, 3.3.7, 3.0.20, 1.1.1zg |
| Siemens | SIMATIC CN 4100 | before V5.0 | V5.0 |
| Siemens | SIMATIC S7-1500 TM MFP - GNU/Linux subsystem | all versions | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.1 | High | NVD |
| CVSS 3.1 | 8.1 | High | CISA (ADP) |
Official description
Issue summary: An uncommon configuration of clients performing DANE TLSA-based server authentication, when paired with uncommon server DANE TLSA records, may result in a use-after-free and/or double-free on the client side. Impact summary: A use after free can have a range of potential consequences such as the corruption of valid data, crashes or execution of arbitrary code. However, the issue only affects clients that make use of TLSA records with both the PKIX-TA(0/PKIX-EE(1) certificate usages and the DANE-TA(2) certificate usage. By far the most common deployment of DANE is in SMTP MTAs for which RFC7672 recommends that clients treat as 'unusable' any TLSA records that have the PKIX certificate usages. These SMTP (or other similar) clients are not vulnerable to this issue. Conversely, any clients that support only the PKIX usages, and ignore the DANE-TA(2) usage are also not vulnerable. The client would also need to be communicating with a server that publishes a TLSA RRset with both types of TLSA records. No FIPS modules are affected by this issue, the problem code is outside the FIPS module boundary.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- github.com/openssl/openssl/commit/07e727d304746edb49a98ee8f6ab00256e1f012b
- github.com/openssl/openssl/commit/258a8f63b26995ba357f4326da00e19e29c6acbe
- github.com/openssl/openssl/commit/444958deaf450aea819171f97ae69eaedede42c3
- github.com/openssl/openssl/commit/7a4e08cee62a728d32e60b0de89e6764339df0a7
- github.com/openssl/openssl/commit/ec03fa050b3346997ed9c5fef3d0e16ad7db8177
Other references
Other vulnerabilities in OpenSSL
- 7.5 High severity
- 7.5 High severity
- 8.2 High severity
- 7.5 High severity
- 7.5 High severity
- 9.1 Critical severity
Recent Use After Free vulnerabilities
- 8.8 High severity
- 8.1 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 7.8 High severity
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