URL, URLSearchParams: throw a RangeError when the percent-encoded result does not fit in a string - #42534
URL, URLSearchParams: throw a RangeError when the percent-encoded result does not fit in a string#42534robobun wants to merge 9 commits into
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…ult does not fit in a string A URL or a serialized URLSearchParams longer than 2^31 - 1 characters aborted the process in WTF::URLParser. oven-sh/WebKit#643 makes the parser give the null URL and adds URLParser::trySerialize. This pins its preview build. - URLSearchParams#toString, and a Request or Response body made from the params, throw RangeError: Out of memory. - new URL, url.href and the URL component setters throw the same error. URL.canParse returns false and URL.parse returns null. - url.searchParams.append and set throw when the URL would not fit, and leave the params and the URL as they were. The URL still takes small changes at its next read. - setSyntheticAllocationLimitForTesting also lowers the limit of WTF's URL parser, so the tests reach it with 1 MiB.
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Status Reproduced on 1.4.3-canary.1+6a92015fc (Linux x64, release). Each line exits 134 with const s = Buffer.alloc(2 ** 29, 0xe9).toString("latin1"); // 512 Mi x "é", 3 GiB when percent-encoded
new URL("http://a/?" + s);
const u = new URL("http://a/"); u.search = s;
const p = new URLSearchParams(); p.set("a", s); p.toString();With this branch each one throws This PR is a draft because it pins a preview build of oven-sh/WebKit#643. When that PR merges, the pin moves to the merged sha and this PR is ready for review. |
WalkthroughThe change adds synchronized URL length limits and fallible error propagation across URL parsing, URL mutation, URLSearchParams serialization, and request or response body conversion. Tests cover boundary lengths, encoded output, rollback behavior, and real allocation limits. ChangesURL overflow handling
Possibly related PRs
Suggested reviewers: Priority: ➖ Normal Severity of issue fixed: Medium Merge Risk: 🟠 High · up to The WebKit preview dependency can disappear and break default builds, so the final merged WebKit revision should be pinned before merge. The new tests also need bounded iteration and repository-compliant string allocation. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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In `@scripts/build/deps/webkit.ts`:
- Line 6: Update the WEBKIT_VERSION constant to reference the merged WebKit
main-branch commit SHA instead of the temporary
autobuild-preview-pr-643-48922538 identifier, preserving the dependency URL
construction behavior.
In `@test/js/web/html/URLSearchParams.test.ts`:
- Line 319: Replace the repetitive string construction in the affected tests of
URLSearchParams.test.ts and the corresponding listed calls in both test files
with Buffer.alloc(...).toString(), preserving each string’s exact contents; use
a latin1 0xe9 fill for the repeated U+00E9 case, matching ASCII fills for ASCII
strings, and a UTF-8-sized allocation for repeated U+4E2D, without applying the
0xe9 fill to other cases.
In `@test/js/web/url/url.test.ts`:
- Around line 851-856: Bound the append loop around params.append in the outcome
callback with a fixed iteration limit that remains above the expected appended
count of 20, while preserving exception capture and the existing appended < 20
assertion.
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📒 Files selected for processing (14)
scripts/build/deps/webkit.tssrc/jsc/URLSearchParams.rssrc/jsc/VirtualMachine.rssrc/jsc/bindings/DOMURL.cppsrc/jsc/bindings/DOMURL.hsrc/jsc/bindings/URLDecomposition.cppsrc/jsc/bindings/URLDecomposition.hsrc/jsc/bindings/URLSearchParams.cppsrc/jsc/bindings/URLSearchParams.hsrc/jsc/virtual_machine_exports.rssrc/runtime/webcore/Blob.rssrc/runtime/webcore/Body.rstest/js/web/html/URLSearchParams.test.tstest/js/web/url/url.test.ts
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std::ranges::count pulls in the MSVC STL's AVX2 helpers, which the Windows baseline scan rejects. The tests follow test/CLAUDE.md for repetitive strings, and the append loop has a bound.
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Updated 12:03 PM PT - Sep 13th, 2026
❌ @robobun, your commit d17d905 has 1 failures in 🧪 To try this PR locally: bunx bun-pr 42534That installs a local version of the PR into your bun-42534 --bun |
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Additional findings (outside the current diff — GitHub can't attach inline comments there):
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src/jsc/bindings/URLSearchParams.cpp—remove()andsort()still callupdateURL()asvoidand drop its newExceptionOr<void>result, so when the associated URL is past the defer threshold and the re-serialized query overflows (the?(((…→%28…=case this PR guards forappend/set),delete/sortmutatem_pairsbut leavem_urlunchanged andm_searchParamsDirtystuck true —url.href/url.searchkeep showing the removed key whileparams.has()says it is gone, where the base branch aborted. Fix: giveremove()andsort()the sameExceptionOr<void>return with apairsBeforerollback on flush failure, likeset().Extended reasoning...
With the 1 MiB test limit:
const url = new URL("http://a/?" + "(".repeat(400000) + "&x=1"); const p = url.searchParams; p.delete("x");.remove()(URLSearchParams.cpp:174-181) drops thexpair fromm_pairs, then callsupdateURL(0)→searchParamsDidChange(0)setsm_searchParamsDirty = true,canDeferSearchParamsUpdate(0)is false (4 * 400_014 > 524_288), andflushPendingSearchParamsUpdate()callstoString()on[{"(…", ""}]→trySerializeproduces ~1.2 M chars and fails → the returnedException{OutOfMemoryError}reachesremove()at line 179 and is discarded (ExceptionOr<void>has no[[nodiscard]], ExceptionOr.h:77). Nowm_pairsno longer containsx,m_urlstill holds…&x=1,m_searchParamsDirtystays true, and every laterhref()read re-attempts the failing 1.2 M-char serialize.sort()at line 110 has the identical shape. On the base branch this same sequence aborts inURLParser::serializeat the nexthrefread; after this PR it silently succeeds with URL and params permanently diverged.append/setwere changed to throw and…Verification: normal —
remove()andsort()still discard the now-fallibleupdateURL()result, so the eager-flush path this PR adds silently swallows the OOM and leavesm_pairsandm_urldiverged. src/jsc/bindings/URLSearchParams.cpp:174-181: ```cpp void URLSearchParams::remove(const StringView name, const String& value) { m_pairs.removeAllMatching(...); updateURL(); //… | normal —…
…that throws leaves the URL clean
A URL keeps a query such as "?(((" as it is, and the params serialize it three
times as long. So the first change of any kind, delete and sort included, can
make the URL too long. All four mutators now go through one helper that puts
the pairs back when the URL cannot take the change.
searchParamsDidChange put the dirty flag on before the flush and left it on
when the flush failed. The next read then serialized the pairs that were put
back, which rewrites a query that the URL had kept as it was.
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The The new test uses the case from the review: |
…DOMFormData::toURLEncodedString The URLPattern canonicalizers and import.meta.resolve use a WTF::URL setter or parse and then read the result without a check. A URL that does not fit in a String is now the null URL, so test() matched an empty pattern and import.meta.resolve returned "". Both now report it: test() and exec() do not match, and import.meta.resolve throws RangeError: Out of memory. DOMFormData::toURLEncodedString and DOMFormData__toQueryString have no caller.
The pending length fits in 32 bits where DOMURL had padding. With a 64-bit member DOMURL grew to 88 bytes, which showed as 2 to 5 % on new URL() in bench/snippets/url-kinds.mjs. The mutators ask the URL once whether it can take the change at its next read. The copy of the pairs, the eager update and the error are in a function of their own that is not inlined.
…uffers an invalid host
More entry points for the same abort, checked against WebKit#643A fuzz run met this abort through entry points that the tests here do not exercise. Three of them are new on main ( Input: Both columns are release builds of main at 55c1106, Linux x64. The second build adds
Eight of the nine stacks end at the Limits of this check:
The rows below |
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Draft: blocked on oven-sh/WebKit#643. The pin here moves to its merged sha.
Problem
URLSearchParamswhose percent-encoded form is longer than a string can be (2^31 - 1 characters) aborts the process:panic(main thread): abort() called, exit 134. Example:new URL("http://a/?" + "é".repeat(2 ** 29)), where eachébecomes%C3%A9.url.search =,params.toString()andnew Response(params)do the same.WTF::URLParser. Its outputVectorand the one inURLParser::serializecallCRASH()past INT32_MAX bytes. TheURLsetters crash inmakeString.Fix
URLParser::trySerialize. This PR pins its preview build.DOMURL, the URL setters (nowExceptionOr<void>) andURLSearchParams::toStringturn that intoRangeError: Out of memory, whichencodeURIComponentthrows for the same input.URL.canParsereturns false,URL.parsereturns null.URLPatternandimport.meta.resolvecheck for the null URL too.url.searchParamschange stays lazy while the URL is sure to fit. Otherwiseappend,set,deleteandsortserialize at once, throw if the URL does not fit, and undo the change.url.test.ts(22),URLSearchParams.test.ts(4),urlpattern.test.ts(5) andimport-meta-resolve.test.mjs(1). 31 fail on 1.4.3. Self-reviewed: 7 concerns raised, 6 addressed, see Notes.Background
WTF::URLis the parsed URL insideDOMURL, the JSURL. The null URL has a null string. A failed parse used to keep its input.DOMURLcopiessearchParamschanges intohrefat the next read (URL: defer searchParams href sync to next read (fix O(N^2) append) #35080). A read cannot throw, so the copy must not fail there.setSyntheticAllocationLimitForTestinglowers the process-wide string limit. It now lowersURLParser's limit too, so the tests need 1 MiB, not gigabytes.Notes
Where this comes from. A fuzzer found it. No user has reported it. The smallest input is a string of about 240 M characters.
Before and after, release build,
s = Buffer.alloc(2 ** 29, 0xe9).toString("latin1"). Before is 1.4.3-canary.1+6a92015fc.new URL("http://a/?" + s),new URL("?" + s, "http://a/")RangeError: Out of memoryurl.search = s,url.hash = sRangeError: Out of memoryurl.pathname = s,url.username = s,url.password = sRangeError: Out of memoryURL.canParse("http://a/?" + s),URL.parse(...)false,nullparams.set("a", s); params.toString()RangeError: Out of memorynew Response(params),new Request(url, { body: params }),fetch(url, { body: params })RangeError: Out of memoryurl.searchParams.append("a", s); url.hrefhrefRangeError: Out of memoryatappendurl.pathname = latin1(2 ** 30),url.username = latin1(2 ** 30)RangeError: Out of memoryurl.search = "#".repeat(2 ** 30)RangeError: Out of memoryurl.search,url.hash,url.pathname= "a".repeat(2 ** 31 - 5)RangeError: Out of memorynew URL("http://" + "a".repeat(2 ** 31 - 8))RangeError: Out of memorynew URL("http://é" + "a".repeat(2 ** 30 + 10) + "/")TypeError: Invalid URLparams.set("a", "a".repeat(2 ** 30))as a Latin-1 string,params.toString()params.set("a", "a".repeat(1.9 * 2 ** 30)),params.toString()Node 26.3.0 for comparison, with 100 M
é(its strings stop at 2^29 - 24 characters):new URL("http://a/?" + s)throwsERR_STRING_TOO_LONG.url.searchParams.append("a", s)returns, and theurl.hrefread after it ends the process with a fatal JS heap out of memory.Other readers of a
WTF::URL. TheURLPatterncanonicalizers andimport.meta.resolvecall a setter or parse and then read the result with no check. With the null URL they read an empty component:test()matched an empty pattern,import.meta.resolvereturned"", and a debug build stopped atASSERT(dummyURL.isValid()). They check now.test()andexec()do not match, andimport.meta.resolvethrows theRangeError.fetch,WebSocket,Bun.pathToFileURLand the module loader already treat the result as an invalid URL.Where the throw is. Bun defers the copy of the params into
href, andhrefis read from getters and from native code that cannot throw. So the mutators keep a bound of what is pending (9 characters for each UTF-16 code unit, 6 for each Latin-1 character). While four times the URL plus that bound is under half of the limit, the change stays lazy, and the later copy cannot fail. The factor four is for a query that the URL keeps as it is and the params serialize longer:(becomes%28=. Past that, each change serializes at once, which is exact. A change that does not fit throws and is undone: the params and the URL are as they were. That includesdeleteandsort, because the first change of any kind serializes the whole query.The setters and the other PRs. The JS bindings already call the setters through
invokeFunctorPropagatingExceptionIfNecessary, soJSDOMURL.cppneeds no change. #40577 makes the same change to the nine setter signatures inURLDecomposition.hfor its own failure (too many pairs). This PR can carry that change: if it lands first, #40577 and #40567 rebase and drop that hunk.Speed. Release builds of main and of this branch, made on one machine, run in turn on one core (
bench/snippets/url-kinds.mjs,urlsearchparams.mjs, and a loop over thesearchParamsmutators).URL.canParseandURL.parse: within 2 % on every row.new URL(): within 5 %, in both directions, which is what two builds of the same code differ by on this machine. A 64-bit member had grownDOMURLfrom 80 to 88 bytes and cost 2 to 5 % onnew URL(). It is 32 bits now, in what was padding.url.searchParams.set()thenurl.href: 250 ns to 198 ns, from the serializer in WebKit#643.searchParamsmutator with no read after it costs 2 to 3 ns more (deleteof a missing name: 25 ns to 28 ns), for the question to the URL and for theExceptionOr<void>that the binding checks.new URLSearchParams(object): the same.Tests. The in-process tests lower the limit to 1 MiB and take 0.2 to 0.5 s each in a debug ASAN build. They cover nine shapes of the constructor (query, path, fragment, username, opaque path, a two-byte string, escaped ASCII, a relative URL, a base URL),
canParseandparse, six setters that percent-encode, every setter on the longest URL the parser takes,searchParams.append,set,deleteandsort(one large value, many values that fit one by one, a query that grows when it is serialized again, and a query that must stay as the URL kept it after a change that throws),toString()at exactly the limit and one past it,ResponseandRequestbodies, fiveURLPatterncomponents, andimport.meta.resolve. Each checks that the URL and the params are unchanged after the throw. A URL that fits still parses, and input that is not a URL is still aTypeError.Four tests need the real limit, because the synthetic one cannot reach these: the parser's buffer past the size where
Vector's growth step gives up,tryMakeStringin a setter, the UTF-8 copy of a string of 2^30 characters, and the#escaping inurl.search. Each runs in a child that commits up to 5 GB and takes 6 to 10 s in a release build. They skip on debug and ASAN builds and below 16 GB of memory.BUN_JSC_validateExceptionChecks=1is clean on the test files.Self-review.
URLPatternandimport.meta.resolvedid not check the URL they read. Fixed, with tests.DOMFormData::toURLEncodedStringhad no caller and still called the crashingserialize. Deleted.append(). That was wrong and is corrected above. It also did not say that only a fuzzer found this. Added.DOMURL.ExceptionOr<void>[[nodiscard]]. It would have caught the dropped results indeleteandsort. It touches every caller insrc/jsc/bindings/webcore, so it is a change of its own.[policy-decision:webkit] gate passed · iteration 0 · 23 files touched
fails on main (without fix)
passes on PR (with fix)
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gate history · 3 passed · 0 rejected · iteration 0
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