Bug 2531354 (CVE-2026-88840)

Summary: CVE-2026-88840 busybox: busybox: TLS ssl_server reads one byte out of bounds when parsing truncated ClientHello
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: security-response-team
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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BusyBox TLS get_client_hello() reads past the end of the input buffer when parsing a truncated ClientHello message.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-09-10 09:49:05 UTC 
A vulnerability exists in the BusyBox TLS server implementation in networking/tls.c. The get_client_hello() function reads p[0] (the compression-methods length byte) after consuming the cipher suite list without verifying that len > 0. A crafted ClientHello that ends immediately after the cipher suite list triggers a 1-byte out-of-bounds heap read.

This is a pre-authentication vulnerability. The one-byte OOB read can potentially leak a single byte of adjacent heap memory or cause a crash in memory-safety-hardened builds.