CVE-2026-29008: U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function

Q: How do I fix CVE-2026-29008?

u-boot: upgrade to 2026.04. Exact commands for each OS are on this page.

Q: Is CVE-2026-29008 being exploited?

CVE-2026-29008 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-29008 affect?

CVE-2026-29008 affects u-boot. Severity is high (CVSS 7.5). U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function (net/tcp.c) that allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet with a manip

Q: How urgent is CVE-2026-29008?

Priority 50/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-29008 is a high-severity flaw (CVSS 7.5) affecting u-boot. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function (net/tcp.c) that allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet with a manipulated data offset field causing payload_len to become negative. When the TCP_SYN_SENT handler calls tcp_rx_user_data() without invoking tcp_seg_in_wnd() validation, the negative payload_len is implicitly conve

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 47%)
CISA exploited list	No
Weakness	CWE-191
Published	2026-07-08
Last modified	2026-07-22

Publisher (CNA): VulnCheck · Vendor: denx

Last updated 2026-07-22 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-08 17:17 UTCPublished CVE record published
2026-07-22 18:32 UTCUpdated Record last modified

denx u-boot UPGRADE

Affected: < 2026.04 · 2026.04 rc1 · 2026.04 rc2 · 2026.04 rc3

Fixed in: 2026.04

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy u-boot || rpm -q u-boot || u-boot --version

2. UPGRADE to 2026.04 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade u-boot

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade u-boot

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-29008?

u-boot: upgrade to 2026.04. Exact commands for each OS are on this page.

Is CVE-2026-29008 being exploited?

CVE-2026-29008 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-29008 affect?

CVE-2026-29008 affects u-boot. Severity is high (CVSS 7.5). U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function (net/tcp.c) that allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet with a manip

How urgent is CVE-2026-29008?

Priority 50/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-46728 HIGH 8.2 UPGRADE Das U-Boot before 2026.04 allows FIT (Flat Image Tree) signature verification bypass because hashed-nodes is o
CVE-2026-29009 HIGH 8.2 UPGRADE U-Boot before 2026.07-rc2 contains a buffer overflow vulnerability in nfs_readlink_reply() (net/nfs-common.c)
CVE-2026-29007 MEDIUM 5.3 UPGRADE U-Boot through 2026.04-rc3 contains an out-of-bounds read vulnerability in tcp_rx_state_machine() (net/tcp.c)

References

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