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stack-buffer-overflow in decNumber #9019

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stack-buffer-overflow in decNumber #9019

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ca3027e
Suggestions for fixing the problem.
ChudaykinAlex May 6, 2026
ed5479c
Merge branch 'master' into work/decNumber_stack_buffer_overflow
Jul 10, 2026
46142e2
Fix decNumber OOB reads and UB found by ASan+UBSan fuzzing
Jul 10, 2026
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2 changes: 1 addition & 1 deletion extern/decNumber/decBasic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1120,7 +1120,7 @@ decFloat * decFloatAdd(decFloat *result,
// the following buffers hold coefficients with various alignments
// (see commentary and diagrams below)
uByte acc[4+2+DECPMAX*3+8];
uByte buf[4+2+DECPMAX*2];
uByte buf[4+2+DECPMAX*2+4];
uByte *umsd, *ulsd; // local MSD and LSD pointers

#if DECLITEND
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3 changes: 2 additions & 1 deletion extern/decNumber/decCommon.c
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Expand Up @@ -461,7 +461,8 @@ static decFloat * decFinalize(decFloat *df, bcdnum *num,
uByte *t=buffer; // safe target
uByte *tlsd=buffer+(ulsd-umsd)+shift; // target LSD
// printf("folddown shift=%ld\n", (LI)shift);
for (; s<=ulsd; s+=4, t+=4) UBFROMUI(t, UBTOUI(s));
for (; s+3<=ulsd; s+=4, t+=4) UBFROMUI(t, UBTOUI(s));
for (; s<=ulsd; s++, t++) *t=*s;
for (t=tlsd-shift+1; t<=tlsd; t+=4) UBFROMUI(t, 0); // pad 0s
num->exponent-=shift;
umsd=buffer;
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