diff --git a/‎Library/Homebrew/test/vulns/semver_spec.rb‎
Lines changed: 21 additions & 0 deletions b/‎Library/Homebrew/test/vulns/semver_spec.rb‎
Lines changed: 21 additions & 0 deletions
diff --git a/‎Library/Homebrew/test/vulns/vulnerability_spec.rb‎
Lines changed: 14 additions & 0 deletions b/‎Library/Homebrew/test/vulns/vulnerability_spec.rb‎
Lines changed: 14 additions & 0 deletions
diff --git a/‎Library/Homebrew/vulns/semver.rb‎
Lines changed: 7 additions & 1 deletion b/‎Library/Homebrew/vulns/semver.rb‎
Lines changed: 7 additions & 1 deletion
@@ -10,6 +10,10 @@
         .to eq [nil, nil, nil, nil]
     end
 
+    it "rejects an oversized prerelease" do
+      expect(described_class.release_version("1.0.0-#{"a" * 251}")).to be_nil
+    end
+
     it "normalises a prerelease with a prefix and build metadata" do
       expect(described_class.release_version("v2026.2.22-rc.1+build.2")).to eq "2026.2.22"
     end
@@ -29,6 +33,23 @@
       end).to all(be_nil)
     end
 
+    it "accepts versions at the input limit" do
+      version = "1.0.0-#{"a" * 250}"
+      expect(described_class.compare(version, "1.0.0")).to eq(-1)
+    end
+
+    it "rejects versions exceeding the input limit on either side" do
+      version = "1.0.0-#{"a" * 251}"
+      expect([described_class.compare(version, "1.0.0"), described_class.compare("1.0.0", version)])
+        .to all(be_nil)
+    end
+
+    it "rejects oversized core, prerelease, build and whitespace inputs" do
+      versions = ["#{"9" * 5000}.0.0", "1.0.0-#{"9" * 5000}", "1.0.0+#{"a." * 2500}a",
+                  "#{" " * 5000}1.0.0"]
+      expect(versions.map { |version| described_class.compare(version, "1.0.0") }).to all(be_nil)
+    end
+
     # From vers gem: basic numeric ordering
     it "orders major versions numerically" do
       expect(described_class.compare("1.0.0", "2.0.0")).to eq(-1)
 
@@ -405,6 +405,14 @@ def range(type, *events)
         .to all(be_nil)
     end
 
+    it "leaves oversized SEMVER boundaries uncheckable" do
+      v = vuln("id" => "TEST-1", "affected" => [
+        affected("npm", "example",
+                 range("SEMVER", { "introduced" => "0" }, { "fixed" => "1.0.0-#{"a" * 5000}" })),
+      ])
+      expect(v.range_status("npm", "example", "2.0.0")).to be_nil
+    end
+
     it "checks an explicit versions list when present" do
       v = vuln("id" => "CVE-1", "affected" => [
         affected("PyPI", "requests", versions: ["2.30.0", "2.31.0"]),
@@ -518,6 +526,12 @@ def range(type, *events)
       expect(v.affects_version?("1.0.0")).to be true
     end
 
+    it "keeps a match when the SEMVER fixed boundary exceeds the input limit" do
+      v = vuln({ "id" => "TEST-1" }.merge(semver_range({ "introduced" => "0" },
+                                                       { "fixed" => "1.0.0-#{"a" * 5000}" })))
+      expect(v.affects_version?("2.0.0")).to be true
+    end
+
     it "matches an open-ended range introduced at v0" do
       v = vuln({ "id" => "CVE-2024-1234" }.merge(semver_range({ "introduced" => "v0" })))
       expect(v.affects_version?("1.2.3")).to be true
 
@@ -5,8 +5,12 @@ module Homebrew
   module Vulns
     # SemVer 2.0 comparison for OSV `SEMVER` ranges (https://semver.org/#spec-item-11).
     # Kept separate from `::Version`, whose ordering differs for prerelease and
-    # build metadata. Minor/patch may be omitted; other spec violations return `nil`.
+    # build metadata. Minor/patch may be omitted; other spec violations or
+    # inputs over 256 bytes return `nil`.
     module Semver
+      MAX_LENGTH = 256
+      private_constant :MAX_LENGTH
+
       CORE_SEGMENT = "(0|[1-9]\\d*)"
       private_constant :CORE_SEGMENT
 
@@ -52,6 +56,8 @@ def self.release_version(version)
 
       sig { params(version: String).returns(T.nilable({ core: [Integer, Integer, Integer], prerelease: T::Array[String] })) }
       private_class_method def self.parse(version)
+        return if version.bytesize > MAX_LENGTH
+
         match = version.strip.sub(/\Av/i, "").match(SEMVER_REGEX)
         return if match.nil?