C1-Ultra: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2025-10263 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in C1-Ultra from Arm, with a CVSS 3.1 base score of 8.4 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. Affected C1-Ultra versions: 0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.54% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of C1-Ultra you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Arm | C1-Ultra | 0 | Not stated |
| Arm | C1-Premium | 0 | Not stated |
| Arm | Neoverse V3 | 0 | Not stated |
| Arm | Neoverse V3AE | 0 | Not stated |
| Arm | Neoverse V1 | 0 | Not stated |
| Arm | Neoverse N2 | 0 | Not stated |
| Arm | Neoverse N1 | 0 | Not stated |
| Arm | Cortex-X925 | 0 | Not stated |
| Arm | Cortex-X4 | 0 | Not stated |
| Arm | Cortex-X3 | 0 | Not stated |
| Arm | Cortex-X2 | 0 | Not stated |
| Arm | Cortex-X1 | 0 | Not stated |
| Arm | Cortex-X1C | 0 | Not stated |
| Arm | Cortex-A710 | 0 | Not stated |
| Arm | Cortex-A78 | 0 | Not stated |
| Arm | Cortex-A78AE | 0 | Not stated |
| Arm | Cortex-A78C | 0 | Not stated |
| Arm | Cortex-A77 | 0 | Not stated |
| Arm | Cortex-A76 | 0 | Not stated |
| Arm | Cortex-A76AE | 0 | Not stated |
| Red Hat | Red Hat Enterprise Linux 10 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 10.0 Extended Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On | Not specified in the record | Not stated |
Version data comes from the organisation that assigned the CVE; 23 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N. Scored by CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.1 | Critical | CISA (ADP) |
| CVSS 3.1 | 8.4 | High | CNA |
Official description
Arm C1-Ultra, C1-Premium, Neoverse V3 & V3AE, Neoverse V2, Neoverse V1, Neoverse-N2, Neoverse-N1, Cortex-X925, Cortex-X4, Cortex-X3, Cortex-X2, Cortex-X1 & X1C, Cortex-A710, Cortex-A78, A78AE & A78C, Cortex-A77, Cortex-A76 & A76A may allow writes to resources owned by a higher exception level.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
How developers prevent this class of flaw
- In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
- Use thread-safe capabilities such as the data access abstraction in Spring.
- Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
- developer.arm.com/documentation/112137
- openwall.com/lists/oss-security/2026/06/09/13
- xenbits.xen.org/xsa/advisory-493.html
- access.redhat.com/errata/RHSA-2026:34911
- access.redhat.com/errata/RHSA-2026:36018
- access.redhat.com/errata/RHSA-2026:36348
- access.redhat.com/errata/RHSA-2026:36349
- access.redhat.com/errata/RHSA-2026:40764
- access.redhat.com/errata/RHSA-2026:47248
- access.redhat.com/errata/RHSA-2026:49031
- access.redhat.com/errata/RHSA-2026:49033
- access.redhat.com/errata/RHSA-2026:51603
- access.redhat.com/errata/RHSA-2026:51604
- access.redhat.com/errata/RHSA-2026:51746
- access.redhat.com/errata/RHSA-2026:52649
Other vulnerabilities in C1-Ultra
- 7.9 High severity
Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities
- 7.0 High severity
- 7.0 High severity
- 7.0 High severity
- 7.0 High severity
- 7.8 High severity
- 7.8 High severity
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