u-boot: Signed to Unsigned Conversion Error
CVE-2026-74220 is a high-severity signed to unsigned conversion error vulnerability in u-boot, with a CVSS 3.1 base score of 8.2 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 2026.10-rc5 as the first without the flaw, so updating u-boot to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.33% 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
- Update u-boot to 2026.10-rc5 or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
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
- LowNo special conditions are needed; the attack works reliably.
- 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
- NoneNo data is disclosed.
- Integrity
- LowLimited modification of data is possible.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.8 | High | CNA (vulncheck.com) |
| CVSS 3.1 | 8.2 | High | CNA (vulncheck.com) |
Official description
U-Boot before 2026.10-rc5 contains a buffer overflow in nfs_read_reply() function in net/nfs-common.c that allows attackers to corrupt memory by supplying crafted NFS READ reply lengths. A malicious NFS server can exploit signed integer handling to bypass length validation and write far past the destination buffer, crashing the bootloader or corrupting memory.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Signed to Unsigned Conversion Error
The product uses a signed primitive and performs a cast to an unsigned primitive, which can produce an unexpected value if the value of the signed primitive can not be represented using an unsigned primitive.
More Signed to Unsigned Conversion Error vulnerabilities (CWE-195)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
Other vulnerabilities in u-boot
- 7.1 High severity
- 8.2 High severity
- 8.2 High severity
- 8.2 High severity
- 9.8 Critical severity
- 7.5 High severity
Recent Signed to Unsigned Conversion Error vulnerabilities
- 8.2 High severity
- 7.5 High severity
- 7.8 High severity
- 7.5 High severity
- 7.5 High severity
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