CVE-2026-74221
HIGH 8.8U-Boot before 2026.10-rc5 contains a buffer overflow in nfs_readlink_reply() function in net/nfs-common.c when processing NFS server responses. A malicious NFS server can send crafted READLINK replies with negative or oversized symlink length values to corrupt memory and crash the bootloader.
Severe if exploited (CVSS 8.8), but no known exploitation and low modeled probability. Patch on a normal cadence.
Exploitation likelihood
0.3%chance of exploitation in 30 days · 27th percentile
Impact if exploited
8.8CVSS 4.0 · HIGH
- ConfidentialityNone
- IntegrityLow
- AvailabilityHigh
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ✓Privileges: No account or privileges required
- ✓User interaction: No user interaction needed
- ✓Complexity: No special conditions — reliably repeatable
- ✓Requirements: No special attack requirements
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept
No public PoC is currently catalogued.
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Data snapshot:
Weakness (CWE)
- CWE-195: Signed to Unsigned Conversion Error
CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
References and research data (JSON)
All CVSS metrics
- HIGH 8.8 v4.0 · CNA Primary
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N - HIGH 8.2 v3.1 · CNA Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H - HIGH 8.8 v4.0 · NVD Secondary
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - HIGH 8.2 v3.1 · NVD Secondary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
References
Patches & mitigations
- https://github.com/u-boot/u-boot/commit/1c0aff3a5fbfeee7a8948f624e0b8554e6e0d8fd CVE record · VulnCheck · Updated 2026-09-29T21:29:23.283Z
NVD · CVE-2026-74221 · Updated 2026-09-30T16:40:50.560
Advisories
- https://www.vulncheck.com/advisories/u-boot-before-2026.10-rc5-buffer-overflow-via-nfs-readlink CVE record · VulnCheck · Updated 2026-09-29T21:29:23.283Z
NVD · CVE-2026-74221 · Updated 2026-09-30T16:40:50.560 - https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-89434 EUVD · EUVD-2026-89434
Technical & other
- https://github.com/u-boot/u-boot/blob/v2026.07/net/nfs-common.c#L643 CVE record · VulnCheck · Updated 2026-09-29T21:29:23.283Z
NVD · CVE-2026-74221 · Updated 2026-09-30T16:40:50.560 - https://github.com/u-boot/u-boot CVE record · VulnCheck · Updated 2026-09-29T21:29:23.283Z
NVD · CVE-2026-74221 · Updated 2026-09-30T16:40:50.560