CVE-2026-6899
MediumCVSS 5.6Exploitation Probability (EPSS)
Low risk1th percentile - higher than 1% of all known CVEs
Summary
The certificate revocation check in the CycloneCrypto cryptographic wrapper of the S2OPC library only considers the first matching CRL, ignoring other valid CRLs of the same CA. This could allow an OPC UA client and server to connect using a revoked certificate.
Risk Assessment
The risk is the possibility of establishing a connection using a revoked certificate, which could compromise trust and security of OPC UA communication.
Recommendation
Update the S2OPC library to a version that fixes the CRL checking logic and verify certificate revocation configuration.
Other vulnerabilities in S2OPC
See all- CVE-2026-67868Critical
A heap-based out-of-bounds write vulnerability exists in S2OPC 1.7.3 in server-side EventFilter handling during CreateMonitoredItems processing. This allows a remote attacker to execute arbitrary code.
- CVE-2026-78049Low
A vulnerability has been found in Systerel S2OPC up to 1.7.3. Impacted is the function SOPC_NodeMgtHelperInternal_AddVariableNodeAttributes of the file src/ClientServer/address_space/internal/sopc_node_mgt_helper_internal.c of the component AddNodes Service. The manipulation of the argument UserAccessLevel leads to out-of-bounds read. It is possible to initiate the attack remotely. A high degree of complexity is needed for the attack. The exploitability is considered difficult. The exploit has been disclosed to the public and may be used. The identifier of the patch is aafbd37d381b618312ebdf5ddf57027f62c14fdd. It is suggested to install a patch to address this issue.
- CVE-2026-67872High
An issue in Systerel S2OPC 1.7.3 allows a remote attacker to cause a denial of service via the event monitored-item queue resize handling.
- CVE-2026-67871High
Buffer Overflow vulnerability in Systerel S2OPC 1.7.3 allows a remote attacker to cause a denial of service via the AddNodes, address_space_bs.c, sopc_node_mgt_helper_internal.c, and toolkit_test_server.
- CVE-2026-67867High
A buffer overflow vulnerability in Systerel S2OPC 1.7.3 allows a remote attacker to cause a denial of service via the Alarm/Conditions wrapper when processing PublishResponse EventNotificationList data.
- CVE-2026-67866High
A buffer overflow vulnerability in Systerel S2OPC 1.7.3 allows a remote attacker to cause a denial of service via the LockedStaMac_ProcessMsg_DeleteMonitoredItemsResponse and SOPC_StaMac_NewDeleteMonitoredItems functions in the client wrapper DeleteMonitoredItems path.
- CVE-2026-67865High
S2OPC 1.7.3 contains an out-of-bounds read in RepublishResponse handling, allowing a remote attacker to cause a denial of service.
- CVE-2026-18257Medium
Improper validity period check for the root issuer certificate in CycloneCrypto cryptographic wrapper of S2OPC allows a certificate issued by this root issuer to be considered trusted even if it is invalid.
- CVE-2026-9758High
Improper comparison with the trusted certificates list in S2OPC allows an attacker to have a well-formed untrusted certificate considered trusted.
Original NVD description (English source)
Check for certificate revocation only considers the first matching CRL and ignores other valid CRLs of the same CA in the CycloneCrypto cryptographic wrapper of S2OPC library. It might allow connection between an OPC UA client and server using a revoked certificate.