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Fixed OOM issue when reading partially corrupted PDFs #20723

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Fixed OOM issue when reading partially corrupted PDFs #20723

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c4db2e6
Improve token reading efficiency in XRef by limiting maximum token le…
akopachov Feb 23, 2026
f56e6c3
Improved ASCII decoding compatibility
akopachov Feb 23, 2026
6003967
Using existing helper method
akopachov Feb 23, 2026
f08d965
Added comment for the magic value
akopachov Feb 23, 2026
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18 changes: 11 additions & 7 deletions src/core/xref.js
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Original file line number Diff line number Diff line change
Expand Up @@ -417,16 +417,20 @@ class XRef {
LT = 0x3c;

function readToken(data, offset) {
let token = "",
ch = data[offset];
while (ch !== LF && ch !== CR && ch !== LT) {
if (++offset >= data.length) {
const MAX_TOKEN_LENGTH = 0x1fffffe8;

@Snuffleupagus Snuffleupagus Feb 23, 2026

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Any "magical" values/constants should always have a good comment explaining why they are needed and how they were chosen.

@akopachov akopachov Feb 23, 2026 •
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Makes sense. Thank you.
I added the comment explaining where and why I picked this magic value from, but I'm open to any discussion if it should be set to some more reasonable value.

@Snuffleupagus Snuffleupagus Feb 23, 2026 •
edited
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Given that PDF.js is first and foremost intended for browsers, using Node.js to choose that value seems a little strange.

Also, please see https://github.com/mozilla/pdf.js/wiki/Squashing-Commits

const dataLen = data.length;
const startOffset = offset;
while (offset < dataLen) {
const ch = data[offset];
if (ch === LF || ch === CR || ch === LT) {
break;
}
token += String.fromCharCode(ch);
ch = data[offset];
offset++;
}
if (offset - startOffset > MAX_TOKEN_LENGTH) {
offset = startOffset + MAX_TOKEN_LENGTH;
}
return token;
return data.subarray(startOffset, offset).toString("ascii");
}
function skipUntil(data, offset, what) {
const length = what.length,
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