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CVE-2025-69420 is a type-confusion vulnerability in OpenSSL TimeStamp Response verification. The signing-certificate attribute processing performed by ossl_ess_get_signing_cert() and ossl_ess_get_signing_cert_v2() accesses an ASN1_TYPE union member without first confirming that its type is V_ASN1_SEQUENCE. A malformed RFC 3161 TimeStamp Response with another ASN.1 type can therefore cause TS_RESP_verify_response() to access an invalid or NULL pointer.
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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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A type confusion vulnerability in OpenSSL TimeStamp Response verification allows an attacker-supplied malformed response to trigger an invalid or NULL pointer dereference and crash the verifying application. The functions ossl_ess_get_signing_cert() and ossl_ess_get_signing_cert_v2() access an ASN1_TYPE union member without validating its type. The description assesses the issue as Low severity because timestamp verification is uncommon and the impact is limited to denial of service; the plugin rates it High, with a CVSS v3 base score of 7.5. OpenSSL 1.0.2 and the listed FIPS modules are not affected.
A vulnerability addressed by the EulerOS_SA-2026-3535 OpenSSL package update; no technical flaw details are provided.
A vulnerability referenced by the EulerOS security advisory; no technical vulnerability details are provided.
A vulnerability addressed by the Huawei EulerOS SA-2026-3825 security update.
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