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fix: accept a negative Set-Cookie Max-Age attribute #5571

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Merged
tsctx merged 3 commits into from
Aug 19, 2026
Merged

fix: accept a negative Set-Cookie Max-Age attribute #5571

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317fc61
fix: accept a negative Set-Cookie Max-Age attribute
arshsmith1 Jul 20, 2026
4403160
fix: check only the Max-Age remainder for non-DIGIT characters
arshsmith1 Aug 11, 2026
55df30d
revert Max-Age step 1 comment to the pinned spec wording
arshsmith1 Aug 12, 2026
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10 changes: 6 additions & 4 deletions lib/web/cookies/parse.js
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Original file line number Diff line number Diff line change
Expand Up @@ -186,17 +186,19 @@ function parseUnparsedAttributes (unparsedAttributes, cookieAttributeList = {})
// If the attribute-name case-insensitively matches the string "Max-
// Age", the user agent MUST process the cookie-av as follows.

// 1. If the first character of the attribute-value is not a DIGIT or a
// "-" character, ignore the cookie-av.
// 1. If the first character of the attribute-value is neither a DIGIT,
// nor a "-" character followed by a DIGIT, ignore the cookie-av.

@tsctx tsctx Aug 11, 2026

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Could you please revert this change? This comment block is intended to preserve the exact wording from the specification.

@arshsmith1 arshsmith1 Aug 12, 2026

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Reverted, the comment block is back to the original spec wording. The code still does the sign-followed-by-digit check but the comment stays verbatim.

const charCode = attributeValue.charCodeAt(0)
const startsWithDigit = charCode >= 48 && charCode <= 57
const startsWithSignedDigit = attributeValue[0] === '-' && attributeValue.length > 1

if ((charCode < 48 || charCode > 57) && attributeValue[0] !== '-') {
if (!startsWithDigit && !startsWithSignedDigit) {
return parseUnparsedAttributes(unparsedAttributes, cookieAttributeList)
}

// 2. If the remainder of attribute-value contains a non-DIGIT
// character, ignore the cookie-av.
if (!/^\d+$/.test(attributeValue)) {

@tsctx tsctx Aug 1, 2026

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Please make the following changes to ensure closer adherence to the specifications.

Suggested change
if (!/^\d+$/.test(attributeValue)) {
if (/[^\d]/.test(attributeValue.slice(1))) {

@arshsmith1 arshsmith1 Aug 11, 2026

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Good call, that reads much closer to the spec. I took the remainder check as suggested and also tightened step 1 to the current 6265bis wording (a "-" followed by a DIGIT). Without that, slice(1) lets a bare Max-Age=- and an empty value slip past step 2 and parse to NaN/0, so validating the sign up front keeps them ignored while step 2 stays the clean remainder check you wanted. The existing edge cases and the -1 case all still pass. Pushed in 4403160.

if (/[^\d]/.test(attributeValue.slice(1))) {
return parseUnparsedAttributes(unparsedAttributes, cookieAttributeList)
}

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15 changes: 14 additions & 1 deletion test/cookie/cookies.js
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Expand Up @@ -449,9 +449,22 @@ test('Set-Cookie parser', () => {
name: 'Space',
value: 'Cat',
secure: true,
httpOnly: true
httpOnly: true,
maxAge: -1
}])

for (const maxAge of ['-', '--1', '-1a', '+1', '']) {
headers = new Headers({
'set-cookie': `Space=Cat; Secure; HttpOnly; Max-Age=${maxAge}`
})
assert.deepEqual(getSetCookies(headers), [{
name: 'Space',
value: 'Cat',
secure: true,
httpOnly: true
}])
}

headers = new Headers({
'set-cookie': 'Space=Cat; Secure; HttpOnly; Max-Age=2; Domain=deno.land'
})
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