diff --git a/Lib/http/cookiejar.py b/Lib/http/cookiejar.py
index 13e5b104a81ea2b..58a53b424daf51a 100644
--- a/Lib/http/cookiejar.py
+++ b/Lib/http/cookiejar.py
@@ -262,10 +262,15 @@ def http2time(text):
     m = STRICT_DATE_RE.search(text)
     if m:
         g = m.groups()
-        mon = MONTHS_LOWER.index(g[1].lower()) + 1
-        tt = (int(g[2]), mon, int(g[0]),
-              int(g[3]), int(g[4]), float(g[5]))
-        return _timegm(tt)
+        try:
+            mon = MONTHS_LOWER.index(g[1].lower()) + 1
+        except ValueError:
+            # Not a real month name; fall through to the slower parser.
+            pass
+        else:
+            tt = (int(g[2]), mon, int(g[0]),
+                  int(g[3]), int(g[4]), float(g[5]))
+            return _timegm(tt)
 
     # No, we need some messy parsing...
 
diff --git a/Lib/test/test_http_cookiejar.py b/Lib/test/test_http_cookiejar.py
index 04cb440cd4ccf66..1691029f5cb2635 100644
--- a/Lib/test/test_http_cookiejar.py
+++ b/Lib/test/test_http_cookiejar.py
@@ -121,6 +121,11 @@ def test_http2time_formats(self):
             '08-01-3697739',
             '09 Feb 19942632 22:23:32 GMT',
             'Wed, 09 Feb 1994834 22:23:32 GMT',
+            # Strictly formatted string with a non-existent month name.  The
+            # month field matches the STRICT_DATE_RE fast path but is not a
+            # real month, and must not leak a ValueError.
+            'Wed, 09 Foo 1994 22:23:32 GMT',
+            'Mon, 01 Aaa 2000 00:00:00 GMT',
         ])
     def test_http2time_garbage(self, test):
         self.assertIsNone(http2time(test))
diff --git a/Misc/NEWS.d/next/Library/2026-07-13-10-30-00.gh-issue-153677.dIxjOG.rst b/Misc/NEWS.d/next/Library/2026-07-13-10-30-00.gh-issue-153677.dIxjOG.rst
new file mode 100644
index 000000000000000..9faf1efd1071dbf
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-07-13-10-30-00.gh-issue-153677.dIxjOG.rst
@@ -0,0 +1,3 @@
+:func:`!http.cookiejar.http2time` now returns ``None`` instead of raising
+:exc:`ValueError` for a strictly-formatted date with a non-existent month
+name. Patch by tonghuaroot.