From 4ebe54529cdce132a12f4a205ff7cc7c3641cda0 Mon Sep 17 00:00:00 2001
From: m-holger <m.holger@qpdf.org>
Date: Sat, 2 Aug 2025 00:50:19 +0100
Subject: [PATCH] Fix linearization logic to conditionally add outlines object only if erased, ensuring robustness against damaged PDFs.

---
 libqpdf/QPDF_linearization.cc | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/libqpdf/QPDF_linearization.cc b/libqpdf/QPDF_linearization.cc
index ce72f98..660290f 100644
--- a/libqpdf/QPDF_linearization.cc
+++ b/libqpdf/QPDF_linearization.cc
@@ -1412,14 +1412,20 @@ QPDF::pushOutlinesToPart(
     QTC::TC(
         "qpdf",
         "QPDF lin outlines in part",
-        ((&part == (&m->part6))       ? 0
-             : (&part == (&m->part9)) ? 1
-                                      : 9999)); // can't happen
-    m->c_outline_data.first_object = outlines_og.getObj();
-    m->c_outline_data.nobjects = 1;
-    lc_outlines.erase(outlines_og);
-    part.push_back(outlines);
+        &part == &m->part6         ? 0
+            : (&part == &m->part9) ? 1
+                                   : 9999); // can't happen
+    if (lc_outlines.erase(outlines_og)) {
+        // Make sure outlines is in lc_outlines in case the file is damaged. in which case it may be
+        // included in an earlier part.
+        part.push_back(outlines);
+        m->c_outline_data.first_object = outlines_og.getObj();
+        m->c_outline_data.nobjects = 1;
+    }
     for (auto const& og: lc_outlines) {
+        if (!m->c_outline_data.first_object) {
+            m->c_outline_data.first_object = og.getObj();
+        }
         part.push_back(getObject(og));
         ++m->c_outline_data.nobjects;
     }
--
libgit2 0.21.4