Unauthenticated stack write via oversized ECDSA signature
Published Aug 20, 2026 · Updated Aug 20, 2026
Out-of-bounds write in Apple SwiftNIO SSH before 0.14.1 allows remote attackers to corrupt stack memory via a crafted SSH message. The SSH message parser copies incoming ECDSA signature integers into a stack buffer without validating their encoded length first, so oversized mpints overwrite memory before public-key or signature verification runs. On servers, any peer that completes the SSH version and KEXINIT handshake can reach the bug without credentials; on clients, a malicious or man-in-the-middle server can trigger it during key exchange. Published sources confirm attacker-controlled stack corruption and process-crash risk, but do not characterize broader post-corruption effects.
Summary
What happened
Out-of-bounds write in Apple SwiftNIO SSH before 0.14.1 allows remote attackers to corrupt stack memory via a crafted SSH message. The SSH message parser copies incoming ECDSA signature integers into a stack buffer without validating their encoded length first, so oversized mpints overwrite memory before public-key or signature verification runs. On servers, any peer that completes the SSH version and KEXINIT handshake can reach the bug without credentials; on clients, a malicious or man-in-the-middle server can trigger it during key exchange. Published sources confirm attacker-controlled stack corruption and process-crash risk, but do not characterize broader post-corruption effects.
The record
- CVE
- CVE-2026-43798
- Published
- Aug 20, 2026
- Updated
- Aug 20, 2026
- Vendor
- Apple
- Product
- SwiftNIO SSH
- Classifications
- CWE-130, CWE-787, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 20, 2026CVE publishedPublication date reported by the CVE source.
- Aug 20, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <0.14.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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