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CVE-2025-69420 is a type confusion vulnerability in OpenSSL's TimeStamp Response verification logic. The flaw is in the code path used by TS_RESP_verify_response(), where ASN1_TYPE union members are accessed without first validating that the underlying type is the expected V_ASN1_SEQUENCE. Specifically, the helper functions ossl_ess_get_signing_cert() and ossl_ess_get_signing_cert_v2() read the signing certificate attribute value without adequate type checking. When a malformed RFC 3161 TimeStamp Response supplies an unexpected ASN.1 type, OpenSSL can dereference an invalid or NULL pointer through the ASN1_TYPE union, causing the process to crash while verifying the response. Affected versions are OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0, and 1.1.1. OpenSSL 1.0.2 is not affected. The OpenSSL FIPS modules for 3.5, 3.4, 3.3, and 3.0 are not affected because the vulnerable timestamp response implementation is outside the FIPS module boundary.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository is a crash-only proof-of-concept for CVE-2025-69420 affecting OpenSSL TimeStamp Response verification. The core exploit logic is in poc.c, a standalone C program that loads a valid RFC 3161 TimeStamp Response, extracts the PKCS#7 signer info, locates the ESS SigningCertificateV2 or SigningCertificate signed attribute, verifies that its ASN.1 type is V_ASN1_SEQUENCE, then deliberately mutates that in-memory ASN.1 type to V_ASN1_NULL using ASN1_TYPE_set(). It then invokes TS_RESP_verify_response() with a trust store containing the TSA certificate. On affected OpenSSL builds, the verification path dereferences the ASN1_TYPE union as though it still contained a sequence, producing a UBSan null member access and process termination. This demonstrates denial-of-service/type-confusion behavior only; there is no remote delivery mechanism, no shell payload, and no code execution logic. Repository structure is minimal and purpose-built. poc.c is the main entry point and only exploit implementation. scripts/prepare.sh generates all local fixtures needed for reproduction: a temporary TSA key/certificate, a data file, a timestamp query, a TSA serial file, and a valid timestamp response using the local OpenSSL CLI. scripts/build.sh compiles the PoC against a user-supplied ASan/UBSan OpenSSL build with libcrypto. scripts/run.sh sets sanitizer environment variables and executes the PoC with response.tsr and tsa.crt. scripts/common.sh centralizes environment setup and validates the local OpenSSL binary and libcrypto path. openssl.cnf and tsa.conf are minimal OpenSSL/TSA configuration files used to create the test artifacts. evidence/confirmed-output.txt contains a shortened sanitizer trace confirming the crash path. The exploit is best classified as a local/file-based PoC rather than a weaponized exploit. It requires a locally controlled vulnerable OpenSSL build and crafted timestamp response artifacts. Fingerprintable artifacts are almost entirely local file paths and configuration references; there are no hardcoded remote IPs, domains, C2 endpoints, or network callbacks in the code.
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37 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A vulnerability in OpenSSL addressed indirectly through upgraded third-party components in Tenable Security Center.
An OpenSSL vulnerability patched by upgrading to OpenSSL 3.6.1 in IPFire Core Update 200.
Unknown (listed among related OpenSSL CVEs, but not described in the content).
Low-severity OpenSSL null pointer dereference in timestamp verification, typically resulting in denial of service when processing crafted timestamp-related inputs.
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Cross-references every affected SKU, including bundled OEM variants.
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