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Fix buffer overflow in Android LogException via std::string concatenation - #1950
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…tion Replace the two strncat(buf, ..., sizeof(buf) - 1) calls in firebase::util::LogException with std::string concatenation, and use a stack-local buffer instead of a non-thread-safe static buffer when formatting log_fmt with vsnprintf. Resolves GitHub Code Scanning security alerts (Rule WS-C-00155): - https://github.com/firebase/firebase-cpp-sdk/security/code-scanning/2786 - https://github.com/firebase/firebase-cpp-sdk/security/code-scanning/2787
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This pull request refactors the LogException function in app/src/util_android.cc to prevent potential buffer overflows by replacing unsafe strncat operations with std::string concatenation, and updates the release notes. The feedback identifies a valid issue where the local buffer buf is left uninitialized, which could lead to undefined behavior if vsnprintf fails; initializing it to zero is recommended.
a-maurice
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Oct 27, 2026
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Description
Resolves GitHub Code Scanning security alerts (
WS-C-00155):In
firebase::util::LogException(app/src/util_android.cc), when formatting a JNI exception message with a non-nulllog_fmt, the previous implementation wrotelog_fmtinto a 512-bytestatic char buf[512]viavsnprintfand then calledstrncat(buf, ": ", sizeof(buf) - 1)andstrncat(buf, message_str.c_str(), sizeof(buf) - 1). Because the third parameter tostrncatis the maximum number of bytes to append rather than the total destination buffer size, a long Java exception message could write past the end ofbuf.This change:
strncatcalls withstd::stringconcatenation (message_str = std::string(buf) + ": " + message_str;).char buf[512]withvsnprintf(buf, sizeof(buf), log_fmt, list)instead of a non-thread-safestaticbuffer.### Upcominginrelease_build_files/readme.md.Testing
python3 scripts/format_code.py -git_diff -noformat_file -verbose.bash scripts/gha/check_copyright.sh -g.Type of Change
Place an
xthe applicable box:https://github.com/firebase/firebase-cpp-sdk/security/code-scanning/2786
https://github.com/firebase/firebase-cpp-sdk/security/code-scanning/2787
Notes
Release Notessection ofrelease_build_files/readme.md.