Use of Externally-Controlled Format String Affecting openssl package, versions [3.4.0,]
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published26 Aug 2026
- disclosed25 Aug 2026
- creditFilipe Casal (Trail of Bits), Brandon Luo, TrendAI Zero Day Initiative
Introduced: 25 Aug 2026
NewCVE-2026-63073 (opens in a new tab)How to fix?
A fix was pushed into the master branch but not yet published.
Overview
Affected versions of this package are vulnerable to Use of Externally-Controlled Format String in ossl_cmp_msg_check_update() in crypto/cmp/cmp_vfy.c. An attacker can crash a CMP client by sending an unexpected response with a sender distinguished name containing format specifiers such as %s or %n. When the client validates a response against an expected sender or pinned server certificate, it converts the peer-supplied DN with X509_NAME_oneline() and passes that string directly to ERR_raise_data(), causing the error-reporting path to treat attacker input as a format string and abort the process.