Description
U-Boot through 2026.04-rc3 contains an out-of-bounds read vulnerability in tcp_rx_state_machine() (net/tcp.c) when CONFIG_PROT_TCP is enabled, allowing remote attackers to read beyond TCP segment boundaries by crafting a malicious packet with a mismatched IP total length and TCP data offset field. Attackers can send a packet with an IP total length of 40 bytes and a TCP data offset claiming 60 bytes of header to cause tcp_parse_options() to read 40 bytes past the end of the TCP segment, potentially corrupting connection state variables such as rmt_win_scale and rmt_timestamp to disrupt TCP window calculations.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| u-boot | u-boot | ≤ 2026.04-rc3 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | u-boot | No fix yet | — |
| Debian 13 | u-boot | No fix yet | — |
| Debian 12 | u-boot | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | u-boot | No fix yet | — |
| Ubuntu 26.04 LTS | u-boot | No fix yet | — |
| Ubuntu 25.10 | u-boot | No fix yet | — |
| Ubuntu 24.04 LTS | u-boot +1 | No fix yet | — |
| Ubuntu 22.04 LTS | u-boot +1 | No fix yet | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | u-boot | No fix yet | — |
| Ubuntu Pro 18.04 LTS | u-boot | No fix yet | — |
| Ubuntu Pro 16.04 LTS | u-boot | No fix yet | — |
Advisories 1
- WID-SEC-2026-2306 DENX U-Boot: Mehrere Schwachstellen BSI CERT-Bund (WID) · Jul 13, 2026
References
- https://y637f9qq2x.com/posts/u-boot-tcp-nfs-vulns/ technical-description exploit
- Mailing List Outreach issue-tracking
- Project Webpage product
- https://www.vulncheck.com/advisories/u-boot-rc3-out-of-bounds-read-in-tcp-rx-state-machine-via-tcp-c third-party-advisory