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Mallory
Medium

OpenSSL openssl dgst silent truncation integrity bypass

IdentifiersCVE-2025-15469CWE-345

CVE-2025-15469 is a flaw in the OpenSSL command-line tool 'openssl dgst' affecting the one-shot signing/verification code path. When used with algorithms that only support one-shot operation, including Ed25519, Ed448, ML-DSA-44, ML-DSA-65, and ML-DSA-87, the tool buffers input with a 16 MB limit. If the input exceeds that limit, 'openssl dgst' silently truncates processing to the first 16 MB and still reports success instead of returning an error as documented. As a result, signatures generated or verified through this affected code path may cover only the first 16 MB of a file while trailing bytes remain outside the authenticated data. The issue affects OpenSSL 3.5 and 3.6, specifically the command-line tool behavior; streaming digest algorithms and library API users are not affected.

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ANALYST BRIEF

Impact, mitigation & remediation

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Impact

What an attacker gets, and what they’ve been doing with it.

The primary impact is an integrity/authenticity bypass in affected workflows. A user may believe that an entire file larger than 16 MB has been signed or verified, while in reality only the first 16 MB was processed. If both signing and verification are performed using the affected 'openssl dgst' one-shot path, trailing data beyond 16 MB can be modified without detection. Verifiers that process the full message via OpenSSL library APIs will reject such signatures, so the risk is concentrated in operational workflows that rely on the vulnerable command-line behavior on both sides. This does not directly provide code execution or privilege escalation, but it can enable undetected tampering of signed content.

Mitigation

If you can’t patch tonight, do this now.

Until patched, do not use 'openssl dgst' with one-shot signing algorithms on inputs larger than 16 MB. Prefer verification implementations that process the full message through library APIs, or use signing workflows/algorithms that support streaming and are not subject to the affected buffering behavior. Where operationally possible, enforce file-size limits below 16 MB for affected one-shot 'openssl dgst' use cases and independently validate signed artifacts with tooling known to process the complete input.

Remediation

Patch, then assume compromise.

Upgrade OpenSSL to a fixed release: 3.6.1 for the 3.6 branch or 3.5.5 for the 3.5 branch. OpenSSL 3.4, 3.3, 3.0, 1.1.1, and 1.0.2 are not affected. Apply vendor-supplied downstream updates where OpenSSL is bundled by an operating system or appliance. After upgrading, revalidate any workflows that use 'openssl dgst' with one-shot algorithms for large-file signing or verification.
PUBLIC EXPLOITS

Exploits

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VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

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VendorProductType
FreebsdFreebsdapplication
OpenSSL Software FoundationOpensslapplication

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Threat actor evidence

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Associated malware

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Detection signatures

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Social activity11

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